small sailboat engine

Yachting Monthly

• Digital edition

Best marine diesel engines: a buyer’s guide

• Sam Fortescue
• September 24, 2021

Modern marine diesel engines may look very similar to the large, noisy, oily chunks of iron of yesteryear, but a lot has changed under the bonnet, says Sam Fortescue

An inboard engine is a critical part of any boat, whether you're a purist who only motors when safety demands, or if you'd rather get into harbour in time for last orders. The chances are you also rely on the engine for battery charging. Credit: WorldFoto/Alamy Stock Photo

Best marine diesel engines: the new tech making inboard engines cleaner, more efficient, lighter and more reliable

Once referred to as the ‘auxiliary’ engine , your boat’s inboard diesel is now so much more than just a helping hand.

Not only is it central to your boat’s ability to manoeuvre safely into tight marina berths, it also allows you to keep up average speeds and make the tidal gate before it closes, charges the batteries that run the ever-expanding suite of entertainment and navigational tools aboard, and keeps the beers cold and showers warm.

Despite visual similarities to the noisy models of yesteryear, modern marine diesel engines are cleaner and more efficient, lighter and more reliable. And they are increasingly interactive.

If you’re considering re-powering your boat, here are some of the key features to look out for.

Marine Diesel Engines: Emissions

Tighter regulation in Europe has been forcing engine manufacturers to reduce the harmful emissions generated by their equipment.

In the marine sector, that means complying with the 2013 Recreational Craft Directive, known as RCD 2, and often with the EPA Tier 3 requirements in the USA.

Though most manufacturers anticipate further tightening in the future, there is nothing yet on the cards for marine diesel engines in the leisure sailing sector.

The focus on reducing emissions has resulted in a better understanding of the combustion process inside the cylinder.

A key pollutant, nitrous oxide, is formed at higher combustion temperatures, so one advance has been to reduce those temperatures.

A mechanical system, like this Beta Marine engine, offers ease of maintenance. You don’t need a laptop to reset the electronics

Increasing the swept volume of the cylinder theoretically creates more power, because there is room to burn more fuel each cycle, but if you keep fuel consumption the same, the diesel generates less heat in combustion.

Another area of development has been around the fuel injection system.

A lot has been written about the desirability and reliability of so-called common rail versus mechanical injection for marine diesels.

As Andrew Growcoot, CEO of Beta Marine puts it: ‘The benefits of a mechanical system [are] simplicity and ease of maintenance. One doesn’t need a laptop to reset the electronics ; a mechanical system is safe and will not power down at the wrong time.’

Beta Marine is a British marine diesel engine supplier that uses a Kubota block, and has no intention of introducing the technology any time soon on sub-100hp engines.

The same is true of France’s Nanni and Spain’s Solé, who both supply good, reliable diesel marine engines to the sailing market.

Hedley Beavis of Solé distributor Engines Plus says research to find a common rail injection system has been delayed by COVID-19.

‘It is not an easy task finding a reliable common rail engine but also at a reasonable price for the marine market,’ he adds.

But while common rail injection makes your engine reliant on an electronic control unit for precise high-pressure fuel injection and makes it more susceptible to poor quality fuel, this widely used technology can also offer significant benefits in terms of power and fuel consumption.

Continues below…

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Plus, it’s quieter and produces less vibration.

That’s because the diesel is injected as a huge number of tiny droplets, greatly increasing the surface area for better combustion.

Common rail injection is usually found on more powerful engines – Volvo Penta uses the system in its D3 engine and above, which starts at 110hp.

But Yanmar took a bold step in 2018 when it launched a new 40hp unit with electronic fuel injection. The 3JH40 is still the smallest marine diesel engine with this technology.

‘Through common rail technology, the 3JH40 offers minimal fuel consumption and exceptionally low noise and emission levels, exceeding EPA Tier 3 and EU RCD Tier 2 emission regulations for virtually smoke- and odour-free operation,’ says marketing manager Sander Gesink.

‘People don’t want to have the smell of diesel onboard making them seasick.’

The demand for more plentiful electrical power on board boats has led engine manufacturers to increase the output of their alternator systems.

Where a typical alternator on a 30hp engine might have been around 50A two decades ago, they are now often in excess of 100A.

So, for example, even Volvo Penta’s entry-level D1-13 engine packs a meaty 115A alternator with its own built-in charging regulator, for optimal battery charging.

The 50hp D2-50 offers the same alternator, as well as the option of expanding output with a pulley take-off for a second alternator.

Even Volvo Penta’s entry-level D1-13 engine packs a meaty 115-amp alternator with a built-in charging regulator

Beta Marine’s 43hp engine comes with a 70A alternator as standard, but can accommodate upgrades to 120A or 175A alternators, as well as a second 175A alternator for really hefty charging.

It is worth noting, however, that many of these alternators remain fairly basic bits of kit with an inflexible charging regime.

That’s one reason that Yanmar has worked with Mastervolt on its 150hp-plus 4LV engines to develop a secondary charging option in addition to the on-board 130A unit.

Using the Alpha III charge regulator, that alternator will put exactly the right charge into the battery bank on a three-step regime that works regardless of the RPM by varying the field current going into the alternator.

Units on smaller, older marine diesel engines can easily be retrofitted with a regulator, such as Sterling Power’s Pro Reg.

Interactive marine diesel engines

It used to be that marine diesel engines would buzz along in the background unless they overheated, in which case you were treated to an ear-splitting alarm from the control panel.

They still do sport their own dedicated warning lights which ping on if oil pressure drops or the temperature rises above a safe 80-90ºC.

But with the growth of instrumentation on board, and the development of fast, bi-directional networks, engine manufacturers have had to up their game.

That means enabling the engine to put data into your NMEA2000 instrument network about its speed, temperature and oil pressure, as well as many other potential parameters on more complex systems.

‘Captains just want to see their engine performance and details on their MFDs,’ says Yanmar’s Gesink.

Steyr’s unique monoblock marine diesel engine starts at 75hp. The MO 4-CYL uses a two-stage unit injection system with the benefits of high-pressure fuel without the requirement for electronic control

As a common rail injection engine, Yanmar’s 3JH40 already has the electronics necessary to connect directly to the boat’s NMEA2000 instrument network, as well as the VC10 electronic throttles and other controls via a J1939 CAN bus.

These include the YD42 smart panel display, which will toggle through engine data such as load percentage and engine hours, as well as standard navigational data like depth and wind speed.

‘Direct connectivity to NMEA and J1939 CAN-bus networks has been purpose engineered into the 4LV range, allowing future-proofed integration to any multifunction bridge display. Same counts for the 3JH40 and the rest of our common rail engine range,’ adds Gesink.

While 110hp-plus Volvo Penta marine diesel engines – the D3 upwards – have been built since 2006 with a proprietary Electronic Vessel Control system, its smaller D1 and D2 marine diesel engines were given a hybrid solution.

This Mechanical Diesel Interface (MDI) is a black box fitted to the side of the exhaust manifold, where heat and vibration have made it somewhat temperamental.

Without the MDI, the engine simply won’t run, although it is quite straightforward to bypass.

Volvo sells an Easy Connect adapter that plugs into the J1939 socket on the MDI and feeds its data out onto a NMEA 2000 instrument network, allowing it to be visualised on the plotter or other displays.

Volvo’s Easy Connect app allows you to monitor engine-specific data over Bluetooth on smart devices

Other manufacturers also offer products that can do this.

Volvo offers dedicated instruments to show fuel level, temperature and voltage if you want it.

It also produces its own glass bridge touchscreen displays from 7in to 24in, although this will mainly appeal to the powerboat market.

More interesting for sailors is Volvo’s Easy Connect app available for smart devices, which allows you to monitor engine-specific data over Bluetooth thanks to the Easy Connect adapter.

Other engine manufacturers have adopted a more agricultural approach.

Beta Marine, for instance, has worked with market-leading sensor firm Actisense to build a module that plugs into the wiring loom that runs between the engine and the control panel, and feeds data into the NMEA 2000 network.

It only works with one of Beta’s more expensive C and CW Deluxe control panels, and requires a bit of splicing in of wires.

Solé also offers an NMEA 2000 converter to get analogue data from the engine into your digital instrument network.

You still need a dedicated control panel, but the SDC2000 kit even allows the engine’s alarms to be transferred to your MFD.

It is compatible with all Solé diesel engines since 2008.

France’s Nanni uses a similar NMEA adapter, but also offers a dedicated interactive display to enhance its control panel – available for all engines above 21hp.

There is a small 4in model, and larger 7in and 9in display built around Raymarine technology, with charting, radar and CHIRP sonar support.

The choice is yours

Every owner will make up their own mind on common rail injection.

It looks like the way of the future, judging by the automotive sector, but critics point out that poor quality fuel and the need for maintenance in out-of-the-way places weigh in favour of mechanical fuel systems.

It depends whether you’ve got far-flung cruising in mind, or whether you plan to stick to home waters.

Weigh up your priorities. The Yanmar’s fuel consumption is certainly better than the competition.

But the Beta offers one of the best torque curves, equating to more usable power at cruising revs.

Thinking about going electric? Click here

Either way, don’t be tempted to overpower the boat, as marine diesel engines are most efficient at around 80% of their revs.

If you want the engine to feed data onto the network, it’s best to know from the outset, so the engineer can hook the whole thing up.

That said, it’s hardly a complex job, although the necessary kit amounts to several hundred pounds in the aftermarket.

If you’re looking to re-power, the key criteria will always be the space available, and access to filters, impellers and freshwater systems for maintenance .

While there’s broad consensus about hydrogen being the fuel of the future, the path to fuel-cell propulsion is distinctly unclear.

In the meantime, alternative fuels may play an increasing part in the energy mix for combustion engines: methanol or ammonia can be stored as liquids and mixed with diesel in a combustion engine.

There are challenges to overcome, not least the nitrous oxides produced when ammonia burns, but there is research time going into just that.

Shipbuilder CMB is working with manufacturers of bigger engines to make the design tweaks to run on dual fuels; focused on the injection system.

A more immediate possibility is the use of hydrogenated vegetable oil ( HVO ) or gas-to-liquids (GLT).

HVO is essentially biodiesel and can be made from waste cooking oil, while GLT is made from natural gas and is said to burn more cleanly than diesel.

‘The advantage of mechanical injection systems is that the engine can take advantage of using low- emission alternative fuels, such as HVO and GLT, without alterations to the engine,’ adds Beta Marine CEO Andrew Growcoot.

Marine Diesel Engines: A buyer’s guide

Volvo penta d2-50.

Volvo Penta D2-50: Easy to get NMEA data from the engine

Volvo has an odd gap in its engine line-up between the 28hp D1 and the 50hp D2, which exist in both shaft and saildrive formats.

The D2 marine diesel engines run at 3,000rpm, which is pretty standard for this power rating.

In general, slower rotation makes for less noise and vibration. Both series use inline injection and feature the MDI electronic interface which has suffered from reliability problems in the past.

On the plus side, the interface makes it easy to get NMEA data out of the engine and onto your instrument network. It also opens up a good range of snazzy remote displays.

Volvo’s ergonomic electronic controls won’t work with the D2 engine, however. They are only compatible with the EVC marine diesel engines that run on common rail injection.

Volvo has excellent, if expensive, global support.

• Power: 51hp (37.5kW) crankshaft
• Cylinders: 4
• Displacement: 2,200cc
• Fuel consumption at max rpm: 11.5lt/hr
• Dry weight: 249kg
• D2-50: £9,360
• Dealers: www.volspec.co.uk ; www.goldenarrow.co.uk

Yanmar 3JH40

Yanmar 3JH40: An award-winning 40ho engine

With a power output rated at 40hp, this hugely successful, award-winning engine was launched in 2018.

Its key feature is the common rail injection system which Yanmar has introduced with claims that it reduces smoke and odour to nearly nil.

This is due to the more complete combustion of the diesel fuel when injected under high pressure.

It also operates at a relatively low 3,000rpm, which makes it quieter than faster-spinning engines, and reduces vibration.

Yanmar has developed a series of digital controls for its engines. The VC10 and VC20 electronic throttles make data such as engine loading available on the network.

There are also dedicated displays like the YD42, which has a full-colour screen. Otherwise, a £350 analogue-to-digital converter will get your engine data onto the NMEA 2000 network.

There’s a saildrive option, which costs some £2,500 more than the shaft alternative.

Yanmar engines are also very well supported with servicing.

• Power: 40hp (29.4kW)
• Cylinders: 3
• Displacement: 1,642cc
• Fuel consumption at max RPM: 8.8lt/hr
• Dry weight: 192kg
• www.barrus.co.uk

Beta 43: Excellent, mid-range torque for its rating

Beta Marine diesel engines are based on the solid Kubota block, and represent good value, no-frills performance.

Painted a distinctive red colour, they offer flexible installation thanks to a good range of options.

This makes them well suited to repowering in tight corners.

Though the design is constantly being improved, this is a traditional mechanical engine with the minimum of electronic gimmickry.

It offers excellent mid-range torque for its rating.

The standard control panels are steadfastly analogue, although a NMEA2000 converter is available to get limited engine data onto the network.

A new digital display panel is now available, with a standard loom input and a NMEA 2000 output.

Reliable and well supported with spares, and readily serviced, these are good engines that are sold worldwide.

• Power: 43hp
• Displacement: 1,999cc
• Fuel consumption at max RPM: 9.3lt/hr
• Dry weight: 238kg
• www.betamarine.co.uk

Nanni N4.43

Nanni N4.43: Low rpm makes for a quieter unit

Nanni, a French-Italian brand, is well represented in the UK by AR Peachment. These distinctive blue marine diesel engines have helped make Nanni the world’s third largest marine engine supplier.

The engines are fairly traditional, with indirect mechanical fuel injection, natural aspiration and water-cooled exhaust manifold. Relatively low RPM makes for a quieter unit.

The N4.43 is in fact a de-rated version of the larger 50hp unit.

Being a mechanical engine, the N4.43 relies on an NMEA adapter to get engine data onto the network.

Though controls remain analogue, the N4.43 is compatible with a series of Nanni digital displays which start at 4in.

Support at the leisure end is not as widespread as bigger brands, but as it’s based on a Kubota engine block, it should be easy to find a competent mechanic.

• Power: 43hp (29.4kW)
• Displacement: 2,197cc
• Fuel consumption at max RPM: 10.3lt/hr
• Dry weight: 228kg
• www.peachment.co.uk

Solé Mini-44

Solé Mini-44: Decent torque at mid range

Spain’s Solé produces a very wide range of diesel marine engines, and the Mini-44 is aimed at yachts in the 10-12m LOA range.

Sam Fortescue is a freelance marine journalist and former magazine editor who sails a Sadler 34, which has taken his family from the Caribbean to the Baltic

It looks cheaper than the competition, but Solé’s model is to quote a fixed price and not engage in the inevitable discounting of the other brands.

This is the smallest four-cylinder unit the company builds, giving quieter running but greater fuel consumption at top speed.

Though rated 42hp, it has a smaller capacity and has to work harder to achieve it.

For that reason it compares better against 38hp models.

A purely mechanical engine, it relies on cam-driven indirect fuel injection and produces decent if not outstanding torque at the mid range.

Available with an impressive range of gearboxes, including saildrive fittings, the Mini-44 is a very flexible engine with lots of options.

A very expensive converter (SDC2000 – £800) is available to transfer the engine’s analogue data into digital signals for your NMEA 2000 network.

But the control panel options, although very attractively styled, remain resolutely analogue.

Solé has decent global support, naturally focused on Europe and the Spanish-speaking world.

• Power: 42hp (30.9kW)
• Displacement: 1,758cc
• Fuel consumption at max RPM: 10.4lt/hr
• Dry weight: 175kg (w/o gearbox)
• www.enginesplus.co.uk

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Engine for small sailboats

Engine for small sailboats : how to choose it.

My projects are focussed on small sailboats, up to about 30 feet, boats on which the choice of the engine often has a heavy impact on the project from several points of view: costs, reliability, weights, effectivness of the propulsion system, safety at sea.

There are currently three main options to power a small (or not so mall, hirundo 750, Petrel 28) sailboat:

inboard diesel engine , both with shaft line transmission or saildrive one

outboard engine on transom bracket

electrical engine, both transom mounted as an outboard engine or fitted in bilge as a traditional diesel inboard one

until two decades ago this triple choice was simply not existent: small 2 strokes outboards were definitely unreliable (on J24 we used to go in and out of the harbour with sails mostly because we were SURE that our engine would have quitted working in the worst possible moment, providing us a plenty of adrenalinic moments…), electrical marine engines simply didn’t exist , so the only possible choice for a small cruising sailboat was a small inboard engine.

Nowadays things are definitely changed: small 4 strokes outboard engine are really sturdy and reliable , electric engine are becoming a reality year after year, and on the other side small diesel engines are stucked on models , technology , costs and weights not so different from 20 years ago, but nonetheless they are really workhorses;

Let’s now consider some of the choice parameters.

idea 19: a 5 HP outboard engine fitted  on transom in central position, a good choice for smallest sailboats

engine has a dramatic impact on total budget on a small homebuilt boat that can be built with a budget of 20-23k euros (hirundo 750, very much less for idea 21 or 19)  , let’s see how much dramatic:

10 hp 4 strokes outboard engine: it costs around 2700 € vat included , and can be purchased basically in each marina, additional costs to fit it on board are low: a plastic gasoline tank with pipes and plugs, a sturdy transom bracket, few bolts and nuts , and you have your powerplant ready to work ; if you want to go for a smaller 5 HP (perfect for Saltaspiaggia or idea 21), engine cost is about 1600 € ; there’s a wide market of second hand engines (pay attention, there are a lot of  “archeological” outboard engines on the market…)

inboard diesel engine : thing become serious for our wallet: a fresh new 10 HP diesel engine fitted with saildrive costs around 7500-8500 €, a shaft line version, just engine and transmission, is about 5600-6500 € , in this case you have to buy also complete shaftline, bracket, propeller, and fitting all the system on board properly requires a good amount of experience (or hiring a mechanic, other costs) , and you even have to buy and fit ancillary systems: fuel tank and filters, exhaust system, and a dedicated engine battery and related wirings ; upgrading from 10 to 20 HP (good choice for bigger boats like Petrel 28) engine cost raises of about 2000 €, both for saildrive models and for shaftline one;

electrical engines: small electric outboards , perfect to power idea 21, costs around 2000€, and other 600-800 € are required  for a spare battery pack, which IMHO a mandatory upgrade; for bigger boats, an electric engine that can be compared to a 10 hp endothermic one , in the 4kW class, can be purchased for around 3700 euros, with no batteries; if you add an AGM battery pack for at least 2 hours of endurance total cost raise to 5700-6700 euros , definitely more expensive than an outboard gasoline engine and not so far from the workhorse diesel inboard engine

use related costs: that is to say , mainly, fuel: given the fact that we’re talking about small engines, fuel rates goes in the order of few liters/hour (tipically 2-3 for 10 Hp diesel inboard and 1.5 for 5Hp outboard engine), so there are not big differences between diesel inboard and gasoline outboard ; of course as long as you have an electric plug in your marina, recharging an electric engine battery pack is free

• servicing: small outboard engines can be taken away form the boat quite easily, so you can service them by yourself in your house’s garden or take them to a mechanic, same thing for electric engine, both outboard and inboard, since they’re quite light ; on the other side, removing a diesel inboard engine is a quite complicated task, and you’ll be forced to service it on board, they’re normally removed only for major overhauling or to be replaced

Reliability

sailboats are made to set on sails and turn off the engine, any sailor know the magic of this moment , but there are several situations in which you have to turn on the engine, even for a good amount of time, and sometimes you have even to push hard your engine: strong tidal streams, strong upwind seas, total zero wind situations (and sometimes even no wind and big waves which is quite annoying), emergency situations due to failures on board and so on; so we need a reliable engine in which we can trust ; I’m not considering here the normal situation in which you’ll turn on the engine for 10-20 minutes to sail away from your marina in calm-normal seas, for this standard purpose each engine is fine; in case of smallest boats, up to 23 feet, I’d anyway go for a electric engine (first choice) or a outboard 4 stroke engine, taking care that our battery pack for the electric engine gives us enough endurance, which may be a decent headache ; for bigger boats, from 23 to 30 footer, diesel inboard engine can be a good choice, and becomes the best choice if you normally need to motor for a quite long amount of time; in this last situation electric engine might be also a good choice but it’d be hugely compromised by the weight of a properly sized battery pack , or by its cost if you go for a light hi tech Litium-polymeric battery pack (they may cost a huge percentage of your entire boat) ; outboard engines often suffer from poor installation on a high placed transom bracket, that may lead the propeller to jump out of the water in short and steep waves with boat pitching, so the engine may be reliable in itself but its set up lead to a unreliable usage (a small well in the cockpit will make the outboard work veeeeery much better, see picture below)

in my humble opinion this is definitely the smartest way to fit an ouboard engine if you have a roomy cockpit : engine is on the centerline, propeller is in a very good position and it can work even with the boat heeled , and if you have to work on the engine you can do it in the cockpit, not hanging outboard in the weirdest positions

inboard diesel engine: Lombardini 20 HP fitted with saildrive on Petrel 28,  an uncompromised classical choice for a mediterranean cruiser

a very neat and clean inboard electric engine fitted on a wooden boat : will this be the future ?

we’ll keep on with this subject in the next part of this post, stay tuned !

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Lightweight and Small Outboard Motors for Sailboats

• By Ed Sherman
• Updated: April 22, 2019

When you’re facing strong winds and you need to get somewhere fast, it’s time to break out a small outboard such as an aluminum genny. A dependable outboard that has enough horsepower to get you to the racecourse and back, yet is light enough not to be a drag on your race results, is invaluable. Most racing sailors don’t need as much horsepower as they might think.

An eight-horsepower outboard, for example, will push a 30-foot, 6,000-pound boat along at 6.5 knots. Anything bigger will weigh more than 90 pounds and isn’t suitable for lifting on and off the stern. Here’s our roundup of some of the best outboard motors for sailboats, and some help in deciphering what’s right for your boat.

We focus our attention on engines available under nine different brand names. Two of the best-known names, Johnson and Evinrude, have dropped out of the small-engine end of the market as part of parent company Bombardier Corporation’s restructuring of these two companies. Currently they’re advertising the availability of six- and eight-horsepower four-stroke models in 2003. Another dropout in the mini-engine market is Suzuki. Their smallest two-stroke is a five-horsepower unit and in the four-stroke configuration, a 9.9 horsepower. Brand and corporate shuffling aside, of particular interest is whether the companies that are building nine horsepower- and-below engines have incorporated four-stroke technology into the lower horsepower range, since it’s now beginning to dominate the mid-sized and larger outboard engine market. The answer to that is yes, to a point.

Two or Four Stroke Outboards for Sailboats

Outboards are either two or four-stroke engines, and the four-strokes have definitely gained favor in recent years for several reasons: they’re quiet, they use much less fuel, and they run more cleanly. Since no oil is mixed with the fuel, the classic two-cycle smokescreen isn’t a factor. In a four-stroke, the piston reciprocates inside the cylinder four times for each power stroke (that is, each time fuel combusts). Rather than opening ports cut into the sides of the cylinder, intake and exhaust valves controlled by a camshaft allow a fuel/air mix to enter the combustion chamber with the suction created by the piston as it moves inward in its cylinder. Exhaust gases are forced out of the cylinder as the piston moves outward.

By carefully designing the camshaft, engineers minimize the amount of time that the intake and exhaust valves are both open, considerably reducing the amount of unburned fuel that exits with the exhaust stream. The end result? Fewer emissions and greater economy.

But they do have at least one distinct disadvantage for the racing sailor, and that’s weight. For example, four-stroke engines in the five-horsepower category are about 20 percent heavier than comparable two-stroke engines of the same horsepower. The good news, however, is that only amounts to between 10 and 15 pounds, depending upon the engine. Four-stroke engines cost more, also, but the improved technology may be well worth it.

If you’re totally weight and price conscious, you’ll want a two-stroke engine. But, if you think you can lose the weight elsewhere, a clean, quiet four-stroke without the hassle of mixing fuel could be the answer. In fact, Mercury/ Mariner’s newest six-horse four-stroke engines are actually 18 pounds lighter than their older two-stroke equivalents–a testament to the benefits of improved design and technology.

Environmental regulations are pushing manufacturers towards four-strokes as well. Four-strokes meet emission control standards, and US Environmental Protection Agency regulations mandate that new outboard and personal watercraft engines reduce engine hydrocarbon emissions by 75 percent by 2006. Environmentally conscious sailors should look for either a C.A.R.B. (California Air Resources Board) “very-low” or “ultra-low” designator, or a specification indicating 2006 EPA compliance.

How Much Horsepower Do You Need?

The amount of power you’ll need depends on several key factors. The first consideration is the weight of your boat. The second is the boat’s wetted surface. Full-keel boats not only weigh more but also have more surface area to push through the water. My rule of thumb here is to start with a two-horsepower engine for small centerboard and keelboats less than 1,000 pounds, and add one horsepower for every 1,000 pounds of displacement. For more exact, albeit complex formulae, I suggest The Propeller Handbook by Dave Gerr (McGraw-Hill 2001).

Compare your boat’s dimensions against what existing classes have found to work; for example, a Melges 24 at 1,650 pounds is typically rigged with a three-horsepower short-shaft engine, while a J/80 at 2,900 pounds can still squeak by with a long-shaft, three-horsepower engine. A 1,790 pound J/22, on the other hand, typically uses a four-horsepower long-shaft engine. On the larger end of boats using outboards, you’ll find the outboard version of the J/29, at 6,000 pounds, requires a 7.5-horsepower long-shaft engine.

If you are intending to do some cruising, or even long deliveries to regattas, an option that’s available on some engines is a high-thrust propeller. On larger boats, this option can save weight over a bigger engine and really make a difference when trying to punch through a strong tide or headwind. High-thrust props cost more and are less fuel efficient–but they can save weight and give you more power.

Once you’ve determined how big an engine you’ll need, the next step is to begin comparing features in the given horsepower range you’ve selected. There are nine manufacturers included in our roundup, but some of their brands are identical products with different labeling. In the smaller sizes, the Mercury and Mariner brands are identical. As for the Nissan and Tohatsu engines, Tohatsu builds them all. Yamaha, Suzuki, and Honda all offer competitive products as well, but they’re all independent brands.

What to Look For in Lightweight Outboard Motors

In the small engine sizes, specific features to look for can be reduced to several key items. For some, having an integral fuel tank will be important. The smallest engines have integral tanks that hold only a quart or two of fuel–good enough for an hour or two of operation. No manufacturer lists fuel consumption because the size boat the engine is pushing and the wind and wave conditions vary widely. Compare the size of the tanks, and whether you can attach a remote tank for longer trips. The extra weight and space of a separate fuel tank will be a burden on smaller ultra-light boats.

The availability of long- and short-shaft versions in the horsepower size you need is also important. Honda for example offers 20 and 25-inch transom height (long or short shaft) right down to their smallest BF2 (two-horsepower) model. Mercury and Mariner only offer a 15-inch short-shaft version on their 3.3- and 2.5-horsepower engines. Shaft length is measured from the top of the bracket to the tip of the shaft–make sure your shaft is long enough to position the propeller and cooling water intake deep enough below the waterline to avoid cavitation when the boat pitches through waves.

Other specifications that are worth comparing are whether the engine is equipped with a simple forward and neutral gearshift or if the unit has a full functioning forward-neutral-reverse gear unit. If you’re going to be doing long deliveries to regattas, or in the larger sizes for a racer/cruiser configuration, consider whether or not a charging system is part of the engine package, and if so, it’s output. Will it be adequate to keep your battery recharged and power things like a tiller pilot and running lights? Also, on the larger engines check to see if electric starting is available, or offered as a standard feature. Having it can be the difference between pain and pleasure.

If you are racing in a strict one-design group, check any class rules that apply to outboard engines. Issues related to brackets, storage of the engine and/or alternative weight might be issues, so be sure to check with your class before making any final decision.

Ed Sherman is the author of Outboard Engines, Maintenance, Troubleshooting and Repair, International Marine/McGraw Hill and a contributing editor to Sailing World.

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Specifications

NOTE: 1 kW = 1.3596 mhp = 1.34102 bhp Fuel condition: density at 15°C = 0.842 g/cm³ Technical data is according to (ISO 8665) / (ISO 3046) Fuel temperature 40°C at the inlet of the fuel injection pump (ISO 8665) Length includes KM35A marine gear (Dimensions may vary with other gears/elbow)

More Information

Winner of the miami 2018 innovation award for the inboard engine category.

The 3-cylinder 3JH40, with an output of 40 mhp, will enable a whole new category of smaller leisure boat owners and commercial vessel operators to benefit for the first time from the efficiency and performance advantages associated with the most recent electronically-managed CR fuel-injection technology.

With an output of 40 MHP @ 3000 rpm (29.4 kW @ 3000 rpm), the 3JH40 is the smallest common rail inboard marine diesel in:

• Displacement, with only 3 cylinders measuring 1.642 L (100 cu in)
• Physical size, measuring 774 x 580 x 632mm
• Weight, measuring 192kg without gear

Through common rail technology, the 3JH40 offers minimal fuel consumption and exceptionally low noise and emission levels, exceeding EPA Tier 3 and EU RCD Tier 2 emission regulations for virtually smoke and odor-free operation.

The 4-stroke, water-cooled 3JH40 is an ideal solution for new builds and repowering applications, specifically monohull sailing yachts and catamarans up to 45ft, small motor boats or sloops, and light duty commercial craft.

*The next largest common rail inboard marine diesel engines are the YANMAR 4JHCR line: 45, 57, 80, 110 MHP.

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Performance Curves Download Specification Datasheet

Standard Engine Package

• Exhaust mixing elbow [L-type]
• Alternator 12V – 125A
• Flexible mounts
• Mechanical throttle sensor
• Fuel pre-filter with water separator
• Fresh water expansion tank
• Belt safety cover

Optional Accessories

• High-riser mixing elbow [instead of L-elbow]
• Secondary alternator 12V – 125A or 24V – 60A
• Extension harness [3m, 5m, 10m]
• Second station
• TFX Sidemount control head
• VC10 Vessel Control System
• NMEA2000 Engine monitoring system
• Semi 2-pole
• SOLAS including Certificate [factory fit only]
• Hot water kit with cocks
• Extension saildrive leg [75 mm]
• Propeller cone nut kit SD60
• On-board spare parts kit

Operation Manual

Product guide, specification datasheet, technical drawings - bobtail, technical drawings - gear, technical drawings - saildrive, compatible products, gears / drives, controls / panels.

Kanzaki Gears

B25 & C35 Panels

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Small Four-Stroke Outboards

Today's small four-stroke engine is still heavier than its two-stroke cousin, but at least prices have come down across the board. consider this field if you need dinghy power or main propulsion..

As most of us know by now, 4-stroke engines are cleaner, quieter, and more fuel-efficient than their two-stroke cousins. A 4-stroke is like an automobile engine—it carries its lubricating oil in a tank, and burns straight fuel in the cylinders. A 2-stroke engine needs oil mixed in with its fuel, and a substantial part of that oil, burned and unburned, is exhausted into the environment. The government has rightly clamped down on such pollution, and marine outboard makers are being forced to move into the 4-stroke arena in order to meet the Environmental Protection Agency’s 2006 emissions standards. The sooner the better, the lighter the better, the more fuel-efficient the better, and the more reasonably priced, the better.

With the ramp-up engineering costs long-since absorbed by the manufacturers, the price of small 4-strokes has dropped within reasonable range of same-power 2-strokes. (The same is not yet true of the bigger four-strokes, unfortunately.)

The bad news is that weight remains a major issue with the small 4-stroke outboard. Some are so heavy they don’t qualify as “portable” engines, in our view. (A 9.9, for example, carries an additional 20 pounds and considerable bulk compared to its 2-stroke counterpart.) The extra weight and size makes the 4-stroke harder to move around, and it can’t be stored as easily—it has to be stored vertically or on one specific side to prevent oil from migrating to the wrong places and damaging the engine.

Still, weighing one thing against another, the future is here, and 4-strokes are the way to go. For sailors considering which 4-stroke might be best suited to their needs, here’s a quick guide.

The Field We rounded up data and specifications on all 4- to 9.9-horsepower 4-strokes currently on the market or slated to be released in 2003.

In total, we collected information on over 30 engines from seven manufacturers. The reality though, is that some engines built by one company are then marketed by another as their own products. This narrows the apparent choices in engines somewhat, but also gives you the option to buy the same engine from a different manufacturer for a lower cost, or from a trusted local dealer.

We looked at and gathered data on most of these small engines at boat shows or dealer showrooms and shops, and also talked with people currently using a small 4-stroke on a dinghy or tender. A few engines, however, were simply not available to us for hands-on inspections, and all data on these were supplied by the makers.

Evaluations consisted of collecting and comparing data from various sources. We did not put any of these engines on boats and run them. Instead, our goal was to build a database of small 4-strokes for the marine consumer to use when selecting an engine for a dinghy, tender or as a kicker—in other words, a “market scan.”

We chased down specifications on all engines and rated each on how easy it is to change the oil. This is an important issue, because even though you don’t have to add oil to the fuel with a 4-stroke, you do have to change the reservoir oil and filter periodically.

Portability is Key We also looked at the portability of these engines. Which ones can a person move more easily and safely from big boat to tender and back; in and out of the station wagon, on and off the kicker bracket on the transom, and so on? Are any easier to store than others, either at home or on board? We look at this from a 4-stroke vs. 2-stoke perspective. In our view, any engine over about 60 pounds is really not very portable, unless you’re an NFL lineman or professional weightlifter.

While inspecting engines at a local marine store, one of our editors had a conversation with a local skipper who has owned and operated a 5-hp Honda 4-stroke on his inflatable for over a year. He travels, and does move the engine off and on the dinghy. He finds the engine quite heavy and unwieldy, making it difficult to transfer from boat to boat. It has nearly gone in the drink on more than one occasion, and since it’s a single-cylinder engine, it doesn’t run as smoothly as he expected.

A number of other boatowners expressed similar opinions about how heavy and cumbersome these engines are to move from boat to boat or dock to boat. We based our portability ratings on these impressions as well as our own findings in hefting these engines at shows and dealerships.

A Word On Pricing No knowledgeable marine consumer would ever pay list price for an engine, but discount prices can vary regionally. They can also vary according to a dealer’s relationship to the manufacturer. For example, with the Bombardier Corporation (makers of Johnson and Evinrude engines), dealers who carry small engines in stock get a 10% discount on the cost of a small engine, versus non-stocking dealers. This means that you will probably be able to make your best deal on the purchase of a small Johnson engine by visiting a dealer that stocks that engine rather than from a dealer that has to order it for you. When we asked Bombardier about this policy, Senior Public Relations Coordinator, Ann Stawski responded, “As to stocking small engines, as always, consumers should consult their local Evinrude and Johnson authorized dealers for the best prices. The factory can only provide MSRP—what price the dealer sells each engine at is up to each individual dealership.”

Accordingly, in this article we’re forced to use MSRP to compare engines on a national basis.

Honda 5 Built by Honda, this single cylinder 4–stroke is the heaviest in its class at 60 lbs., and carries the highest list price as well. Its cowling lacks the curvaceous styling of its bigger siblings, and like all the engines in this review can only be stored vertically or on one specific side.

The Honda 5 has two “rests” built into the case to facilitate storage on that side of the engine. An oil change on this engine is simple, but the oil drain is located on the bottom of the engine block, which makes for oily hands when removing this plug. We’d like to see an oil drain located on the side of the engine like the plug for changing the lower unit oil. No oil filter is installed, so there’s no filter to change or clean.

Bottom Line: A little heavy and a little pricey compared to the competition.

Honda 8/9.9 This Honda two-cylinder carries either an 8 or 9.9 horsepower rating. When purchased as an 8, this engine ranks a little high on both weight and list price as compared to other 8-hp competitors. However, as a 9.9 this engine is the lightest in its class. In either hp rating the engine is quite stylish, with a smoothly rounded appearance. Like the 5, two rests are built into the case to allow for one-sided storage. We like the spin-on oil filter, but don’t like the fact that removal of an engine lower side panel is required for access to service this filter. Even though this engine is the lightest in its class when rated at 9.9 hp, at 87 pounds it’s still virtually impossible to handle over water, especially in a tippy boat. It rated poorly on portability.

Bottom Line: If you must have this much power on your inflatable, this engine, with its good looks and light weight (for its horsepower) should fit the bill. But it’s better as a transom auxiliary on a fair-sized sailboat.

Johnson 6 This Bombardier-built 4-stroke totes the heftiest list price in the 6-hp class. The Johnson 6 comes equipped with a front-mounted shifter and is available with a 15″ or 20″ shaft. For a 6, it is bulked up at 68 pounds—over our weight limit for portability. An oil change on this engine requires the removal of an engine lower side panel to access the filter.

Bottom Line: This engine is so heavy for its horsepower we would not give it serious consideration for purchase. But it’s a lot lighter than the Yamaha 6.

Johnson 8 This two-cylinder built by Bombardier ties with the Yamaha F8 for the lightest weight in the 8-hp class at 83 pounds. It is available in 15″ or 20″ shaft lengths and has a front-mounted shifter. We prefer front or tiller mounted shifters to side mount simply because it puts a critical engine control within easy reach. An oil change on the 8 requires the removal of a lower side panel to access the filter for servicing. This procedure is recommended by Johnson for each oil change, we would like to see the filter relocated to alleviate this added step.

Bottom Line: This is the most competitive engine in the Johnson line, tied for lightest and priced within $90 of the lowest.

Mercury 9.9, Mercury 9.9 Bigfoot, Mercury 9.9 Sail Mercury builds this 2-cylinder engine by combining its own lower unit with a Yamaha power head. It’s available in several standard configurations; we looked at the basic 9.9, the 9.9 Sail, and the 9.9 Bigfoot. The basic 9.9 with a 15″ shaft ranks as the least expensive in its class, with the only MSRP under $2,000. It displaces nearly 20 cubic inches and tips the scales at a hefty 111 lbs. in the basic configuration.

The Bigfoot is bulked up even more with electric start, a higher ratio gearbox, and a 20″ shaft, giving it an all-up weight of 128 lbs. The higher 2.42:1 gear ratio allows it to use a larger slower-turning prop than the basic engine, making it better suited for a larger, heavier boat. The Sail version has all the features of the Bigfoot, plus a 25″ shaft, making it the heaviest engine listed at 133 lbs. We just can’t view these engines as portable. It really is a two-person job to remove or install one of these bruisers. Service on the Mercury 9.9, however, is as easy as it gets: The oil filter is a spin-on that is accessible without removing anything except the engine hood.

Bottom Line: Although this engine is in our opinion not portable, we like the optional configurations available, each designed for specific uses.

Suzuki 4/6, Johnson 4 This single-cylinder 4-stroke built by Suzuki (new for 2003) can be purchased with a 4- or 6-hp rating. Bombardier markets the 4-hp version as the Johnson 4. All 15″ shaft versions weigh in at 55 lbs., which is manageable for the average boater. We like the 6-hp version best. It has a 50% increase in power without any increase in weight. Suzuki achieves this with a slightly larger carburetor, some engine timing changes, and a higher maximum rpm. It is available in 15″ or 20″ shaft lengths, has a side-mounted shifter, and resting pads on the port side for storage. The integral fuel tank has a capacity of just under a half-gallon. An optional external fuel tank can be added. No oil filter is installed, making an oil change a simple drain and fill.

Bottom Line: We prefer this engine in the Suzuki 6-hp configuration; it ranks among the best in class for power to weight.

Suzuki 9.9, Johnson 9.9 Suzuki’s twin-cylinder 4-stroke is marketed as the 9.9 and the 15 (not covered here). Bombardier also markets this engine as the Johnson 9.9. It’s one of the lighter 9.9s we reviewed at 97 lbs. It’s available in 15″ or 20″ shaft lengths and with or without an electric starter. Each oil change on this engine requires the removal and cleaning of the oil screen, and the change requires the removal of a lower side panel.

Bottom Line: The extra work of removing and replacing a side panel on every oil change is a hassle, and it’s difficult to know why one would buy the Johnson version over the Suzuki version—it’s priced over $500 higher. The only reason we can think of would be better dealer access.

Tohatsu, Nissan,Mercury 4/5/6 This Tohatsu-built single cylinder is marketed as nine different engines by three makers. All the 4s have integral fuel tanks and the bigger versions don’t. Tohatsu increases the horsepower from the base engine with changes to the carburetion and boosts in the maximum rpm. This engine, when marketed by Tohatsu, carries the lowest MSRP in each horsepower range it fills. In place of the pair of resting pads most engines carry, this engine lies on the tiller handle and a single pad. All weigh in at 55 lbs. with a 15″ shaft, and a 20″ shaft is also available. The oil drain plug is located on the bottom of the engine block and is not as accessible as we’d like. There’s no filter though—just a drain and fill oil change.

Bottom Line: If you can find a Tohatsu dealer in your area we think you’ll get the best price on this engine. The upside when buying from Mercury is its extensive dealer network.

Tohatsu 9.9, Nissan 9.9 The Tohatsu-built two-cylinder, also marketed as the Nissan 9.9, displaces a whopping 20 cubic inches and weighs in at an equally impressive 114 lbs., the heaviest 9.9 surveyed. It is available in 15″ and 20″ shaft lengths and is within $50 of the lowest cost 9.9 on the market—the Mercury. An oil change on the Tohatsu is a drain and fill, plus a readily accessible spin-on filter.

Bottom Line: This heavyweight lives by the racer’s credo: When you need to make horsepower there is no substitute for cubic inches. We like the price and online manuals. But unless you’re in monstrously buff shape, or have a friend around at moving time, this heavyweight is best for permanent mounting.

Yamaha 4 This single-cylinder by Yamaha is by far the lightest in its class at 48 pounds. It’s available in 15″ or 20″ shaft lengths and carries about one-third of a gallon of fuel in an integral tank. Its list price is at the upper end of the range in the four horsepower class—only the Johnson 4 is priced higher. An oil change is a simple drain and fill; no filter is installed.

Bottom Line: If your boat is particularly weight-sensitive , or you need to take the engine off frequently for racing or security, or if you have a small dinghy used strictly as a putt-putt utility boat and don’t care about speed, this would be an engine of choice.

Yamaha 6/8 Yamaha markets its newest twin cylinder 4-stroke as both a 6- and 8-hp engine. In the 6-hp class it’s a behemoth, weighing almost 30 pounds more than the lightest of the group. But, as an 8 it’s tied for lightest with the Johnson 8, at 83 lbs.

This is the latest entry in the 4-stroke field for Yamaha and sports several ergonomic improvements. The tiller handle is significantly longer than others and the shifter is on the tiller and is very close to the throttle. This allows an operator to stand up in a dinghy for better visibility and still reach the throttle with ease. It is also equipped with a freshwater flush adapter to rinse the engine of saltwater without using “ears” over the raw-water intakes.

Both versions are available with a 15″ or 20″ shaft and have an electric-start option. A high-thrust version of the 8, suitable for bigger, heavier boats is also available. It has a beefier transom bracket, a 20″ or 25″ shaft, and an increased gear ratio of 2.92:1. This enables it to use a larger, slower-turning propeller. The oil drain on this engine, which is readily accessible, is located on the lower unit. No serviceable filter is installed.

Bottom Line: We like the features added by Yamaha to improve the ergonomics of this engine. In the 8-hp class the weight is as good as currently available. As a 6-hp, it’s quite heavy.

Yamaha 9.9 The 9.9 from Yamaha doesn’t have all the recent improvements of its little brother. It is a straightforward engine available in two configurations, the standard and the high-thrust. The basic 9.9 is available in 15″ or 20″ shaft lengths with or without an electric starter and weighs in at 91 lbs. in its short-shaft version. One thing we don’t like is the side-mounted shifter. It’s the only engine in this class that still sports this design, which just isn’t as convenient as the front- or tiller-mounted shifts. Oil changing this engine requires the replacement of a spin-on filter, accessible by removing the engine’s hood.

Bottom Line: Like the Mercury 9.9, this engine is available in a geared-down version suitable for larger boats. It’s lighter than the Mercury but costs a bit more.

Conclusions There’s no question that we should make the move to 4-stroke technology to support the environment. Thenew engines are reliable, quiet, fuel-efficient, and simple to run. You don’t have to carry a separate oil supply or go through all that tedious measuring at the gas dock. And these days the price is right, or right enough.

At least for the foreseeable future, though, a 4-stroke engine will be considerably heavier than its 2-stroke cousin, and more difficult to stow. In trying to figure out which engine to buy, consider your power-to-weight requirements. If you replace the 60-pound 2-stroke hanging on your transom with a 4-stroke that weighs 20 pounds more, what will happen to your trim? Will you still be able to muscle it on and off? Can you afford a reduction in horsepower to offset the added weight?

For dinghy power the choice becomes more complex, involving not only the weight and trim of the boat and how often you contemplate having to move the engine on and off the transom, but your intended uses of the dinghy. It’s always a balancing act. Some sailors who anchor out like to have the biggest outboard they can fit, because a 1/2-mile ride through a headwind and chop in an underpowered dinghy can be unpleasant at best and impossible at worst. Larger engines can be raised and lowered with the help of a sling rigged to a halyard-supported boom—but try it in rough water, and the idea of being able to step aboard the dink with a nice light engine in one hand becomes more appealing.

There’s also the consideration of engine repair in far-flung places. Some long-distance cruisers tell us they’ll stick with 2-strokes until outboard mechanics everywhere know how to fix the 4s, and have parts available.

Also With This Article Click here to view “Value Guide: 4-6 HP Four-Strokes.” Click here to view “Value Guide: 8-10 HP Four-Strokes.” Click here to view “Ratings: 4-10 HP Four-Strokes.”

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Portable Outboards

Every sailor knows that operating and maintaining a diesel engine in a saltwater environment can be a challenge. Add to that the fact that many of these engines are upwards of twenty years old and may have a sketchy maintenance record. Enjoying sailing can often translate to being a part-time diesel mechanic .

Well, that’s where SaltWaterDiesels.com kicks in to gear. Here you can learn how to maintain, troubleshoot and repair your sailboat’s small marine diesel engine. There’s a little bit of history about the development of the diesel engine and some general advice about maintaining your engine.

We passionately believe that if you know how it works, then you will know how best to fix it.

This means that if your engine gives you trouble when you’re at sea, you have at least a fighting chance of getting it working again yourself. Self-sufficiency at sea (in this case the ability to solve minor engine problems) is the hallmark of a good skipper.

Let’s begin. Choose your engine by manufacturer…

The semi-diesel, or hot-head, engine is not a true diesel, but retains the operating functions of the diesel with the exception of high compression. On these engines, the head or a bulb in the combustion chamber is heated to near red heat, usually with a kerosene torch. The engine usually has a manual pump that will force an amount of fuel that will be sprayed through a nozzle in the combustion chamber against the heated area. As the engine is rolled against compression, the manual pump is activated and the sprayed fuel ignites. This in turn creates pressure in the combustion chamber against the piston, thus starting the engine.

Once the engine starts, fuel addition, under pressure, continues automatically and is controlled by the governor. As in a true diesel, the engine speed is controlled by the timing and length of fuel addition, during the power stroke. Also, as in the true diesel engine, this has no throttle on the air intake. Most semi-diesel engines are 2-stroke but there are 4-stroke versions also.

In a semi-diesel, once the engine starts the heat source for the hot-head or bulb can be removed; the heat is generated by the combustion itself to continue the ignition process. Typically, semi-diesel engines have from 5:1 to 7:1 compression ratios. They can use a variety of liquid heavy fuels, from kerosene to heavy bunker oil, and almost anything in between. Their ignition does not come from the pressure generated by the engine as a true diesel does.

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The VOLVO PENTA MD4 is a marinisation of the Mercedes-Benz OM636 engine.

This version is also fitted with a BOWMAN heat exchanger but uses a different sea-water pump.

Front Projection

Side Projection

Side Projection with Sail Drive

The Solubility Rules of Salts

1. The nitrates, chlorates, and acetates of all metals are soluble in water. Silver acetate is sparingly soluble. 2. All sodium, potassium, and ammonium salts are soluble in water. 3. The chlorides, bromides, and iodides of all metals except lead, silver, and mercury(I) are soluble in water. HgI2 is insoluble in water. PbCl2, PbBr2, and PbI2 are soluble in hot water. The water-insoluble chlorides, bromides, and iodides are also insoluble in dilute acids. 4. The sulfates of all metals except lead, mercury (I), barium, and calcium are soluble in water. Silver sulfate is slightly soluble. The water-insoluble sulfates are also insoluble in dilute acids. 5. The carbonates, phosphates, borates, sulfites, chromates, and arsenates of all metals except sodium, potassium, and ammonium are insoluble in water but soluble in dilute acids. MgCrO4 is soluble in water; MgSO3 is slightly soluble in water. 6. The sulfides of all metals except barium, calcium, magnesium, sodium, potassium, and ammonium are insoluble in water. BaS, CaS, and MgS are sparingly soluble. 7. The hydroxides of sodium, potassium, and ammonium are very soluble in water. The hydroxides of calcium and barium are moderately soluble. The oxides and hydroxides of all other metals are insoluble.

seriesOne Installation Guide

The following is a brief description of a typical seriesOne installation. Detailed instructions are included with each product and should be followed closely.

• Remove shaft from transmission coupling.
• Disassemble and remove all of the existing shaft sealing system.
• Remove the hose clamps and old hose from the shaft log (stern tube). Discard them. DO NOT RE-USE these components as they will not function correctly with the Seal.
• Draw the shaft back up against the coupling. This will expose the portion of the shaft that was located under the old hose and stuffing box.
• Insert the end of the seriesOne unit into the articulated hose and push in as far as it will go.
• Position the seriesOne Unit while installed in the articulated hose next to the stern tube to determine approximately where the lip seal will ride on the shaft.
• Examine this area carefully. Be SURE that it is free of pitting, nicks or surface imperfections which could cause leaking. Clean this area thoroughly. Polish the shaft using 280 to 320 grit wet/dry sandpaper or emery cloth working around the shaft. Fore and aft actions could put flats or grooves in the shaft. Do NOT over polish the shaft or this will prevent the lip seal from sealing out the water. The assembly may be shifted forward slightly by adjusting the position of the hose on the stern tube at the time of installation.
• Carefully press the red seal protector into the front of the seriesOne. Make certain it covers the “lip” portion of the seal.
• Back the shaft away from the coupling to provide enough room to install the assembly.
• Carefully slide the assembly (hose-end first) onto the shaft so that the shaft passes through the red seal protector.
• Slide the assembly down the shaft and onto the stern tube. Push on as far as it will go or as needed to position the lip seal on a clean spot on the shaft. Make sure the hose is over the stern tube enough to be able to put both hose clamps on.
• Reconnect the shaft to the coupling. Make certain the coupling is firmly secured to the transmission.
• To help align the unit, grasp the assembly and slide it forwards on the stern tube an inch or so and rotate it side to side twice. Slide the assembly back into position on the stern tube. Space the two hose clamps over the stern tube end evenly and “snug”. Hose clamp screws should be on opposite sides to distribute the pressure evenly. Space the two clamps on the seriesOne end of the hose evenly and “snug”. Confirm that both the seriesOne shaft seal and stern tube are fully inserted into the articulating hose. Tighten all four hose clamps.
• Pull the red seal protector from the Seal. Separate the tabs to split the cone and remove it from the shaft.
• Connect the seriesOne to a pressurized water supply source (point in the engines raw water cooling system) by attaching the water injection hose to the stainless steel fitting on the housing. CHECK WATER SUPPLY TO SERIESONE BEFORE OPERATING VESSEL  (1 gallon per minute at idle)
• *** NEVER USE GREASE OF ANY KIND ***

Cutlass Bearing or Cutless Bearing

In short, Cutlass is a type of curved sword and Cutless is a type of rubber bearing although the two are often mixed up.

This type of bearing originated in USA and was manufactured in the 1960’s by a company called Johnson Cutless  which is still a registered trade  name.The  bearings seem to be marketed by  DURAMAX  who sell them as  “Johnson Duramax Cutless Bearings” . In the USA they are still referred to by the full title but others seem to have resorted to the shorter “Cutless Bearing”.

Some insist that the Cutless brand name was a play on words – that they “cut less” than other rubber bearings as the grooves let grit out like the flutes of a drill. Perhaps.

Why do engines need air intake silencers?

Surely, you might ask, the noise of an engine comes from the exhaust output and not from drawing air in. Well, imagine for a moment the air being drawn into the cylinders of your marine diesel engine. The column of air flowing into your cylinder moves along the pipework rapidly while the valve is open during the intake stroke, and then abruptly stops in its tracks when the valve shuts. The moving column of air suddenly stops flowing in to the engine, compresses a little and bounces back like a spring. This pressure wave travels backward at the speed of sound until it meets a hard surface in the pipework, and then it bounces back toward the cylinder. The air intake then acts like a loudspeaker pumping out vibrations. The pressure wave actually bounces back and forth two or three more times before the intake valve opens again. Just as in a recording studio, these echoes are trapped by closed cell foam in your air intake silencer.

Engine Belts

The crankshaft, usually the pulley wheel at the bottom of the engine, usually drives the belts. Belts transfer power to other pulley wheels on the engine and drive the alternator, to provide power to the batteries, and the water pump to circulate cooling water around the engine.

If the belt is too loose:

The alternator may be inefficient resulting in uncharged batteries. The water-circulating pump may be inefficient resulting in the engine running hotter. Regularly checking gauges such as the voltmeter and engine temperature will highlight both of these problems.

A slipping or loose belt is often visually indicated by black belt dust around the engine near the pulleys. There are two common types of belt; flat belts or ‘V’ shaped. Consult your owner’s manual about their accurate testing and adjustment, but a common rule of thumb to check adjustment is:

• V Belts can be deflected by about 12mm and no more.
• Flat belts should be able to twist through 90 degrees and no more.
• A belt adjusted too tight can put excess pressure on the pulley wheel shaft and increase wear on the shaft bearings of the pulley wheels.

The Volvo Penta MD2030 is what Perkins calls a 103-10. Perkins in turn imported these 100 series engines from a Japanese company called Ishikawajima Shibaura Machinery, Ltd. ISM is part of Ishikawajima Harima Industries, one of Japan’s largest industrial companies.

Perkins marketed this engine in a marinized version as the Perama M30. They sold the engine to Volvo Penta who marketed it as their MD2030. They also sold the engine to Massey Ferguson, McCormick, Terramite, Textron, Jacobsen, Cushman, Vermeer, Leech Lewis, JCB, Kobelco, and Northern Lights to name just a few. In the US, the engine was distributed thru Detroit Diesel – Allison which is closely tied to the MTU conglomerate. By 1996, Perkins had become so successful at marketing these engines to other equipment manufacturers that they formed a joint venture with ISM called Perkins Shibaura Engines, Ltd. and began assembling the engines at the Perkins facility in Peterborough, UK from parts shipped from Japan. In 1997, Perkins was acquired by Caterpillar. With an added boost from Caterpillar, this little engine has become one of the most popular engines in the world. It’s used in turf equipment, tractors, mini-excavators, brush choppers, compressors, welders, pumps, generators and many other applications. Even Caterpillar uses it in some of their smaller equipment. The “Perkins” name was highlighted on the engine ID plate which is located on a distinctive boss just forward of the injection pump. The 2006 model year’s production of the engine has “Shibaura” highlighted on the ID plate. In 2001, the larger Shibaura 400 series engine was introduced with assembling at Peterborough, UK from parts mostly from Japan, and in June, 2004 assembling of the 400 series engine began at a Caterpillar facility in Griffin, Georgia, USA with production exceeding 100,000 units per year.

How do sacrificial anodes work?

When two dissimilar metals are in contact (electrically connected), and immersed in an electrolyte (such as salt water) they produce a galvanic cell (like a battery). As current (that is, electrons) flows from one metal to the other, the metal donating the electrons changes form and corrodes. This process is called galvanic corrosion and will quickly destroys underwater metals.  The way we counteract galvanic corrosion is to add a third metal into the circuit, one that is less noble than the other two to give up its electrons. This piece of metal is called a sacrificial anode, and in marine engines it is most often made from zinc.

You will, no doubt, be familiar with the shaft anode shown above. The stainless steel of the shaft will cause the Bronze of the propeller to corrode, and so we install a zinc sacrificial anode to prevent this happening. Metals can be placed on a scale – the galvanic scale – to let us know which will sacrifice themselves in any pair. If two metals are in contact in an electrolyte (such as salt water) then the metal which is higher up the Galvanic Scale will corrode. You will notice that Zinc is second from top.

Heat exchangers in marine diesel engines are typically fabricated from a mix of copper alloy and mild steel. These are at risk of galvanic corrosion. To combat this, many heat exchangers are fitted with a zinc “pencil” anode. You will find it usually under a plug or plate within in the exchanger. The pencil is unscrewed from the plug for replacement. Raw water cooled engines have a similar zinc anode inside the cooling-water jacket to protect dissimilar metals in the engine. Determine if your engine and heat exchanger are fitted with internal anodes, and if so, check them at least annually. If they are half depleted then best replace them.

Diesel bug is contamination of diesel fuel by microbes such as bacteria and fungi. Water can get into diesel fuel as a result of condensation, rainwater penetration or adsorption from the air — modern biodiesel (a mix of diesel from fossil fuel and oil from plants) is especially susceptible to water absorption. The presence of water then encourages microbial growth which either occurs at the interface between the oil and water or on the tank walls, depending on whether the microbes need oxygen. Dead bacteria, fungus and their waste products result in a sludge which generally lies at the bottom of the fuel tank. In rough weather, however, this sludge can get mixed up into the fuel and sucked into the primary fuel filter, which can cause fuel starvation and your engine stopping in, remember, rough weather – just when you need it.

There are additive treatments which help to reduce the occurrence of diesel bug.  One example is Hydra FuelPlus biocide which “rapidly eliminates all microbial contamination, bacteria, algae and fungi present in fuel tanks without effecting the fuel quality. It stops microbes and promotes trouble free combustion, reduces smoke emissions and improves engine efficiency.” As with most biological growths, Diesel Bug is a temperature related problem and some areas of the world are more susceptible than others. Speaking to your fellow boat owners will help understand the risk in your area.

Remember, the treatment will kill the bug but it will not clear away the sludge. If you have had an infestation in your diesel tanks, then polishing your diesel and steam-cleaning your tanks is the best way to eliminate the residue.

Diesel School – What is Bio-diesel?

Bio-fuels used today are largely derived from agricultural crops. Sugar cane and corn are used to make ethanol which is mixed with petrol for road vehicles, while bio-diesel is made from vegetable oils like soy. As a renewable resource these products have a positive effect on environmental damage caused by fossil fuel use as they consume carbon dioxide from the atmosphere as they grow. Critics point out, however, that food prices have increased in less developed parts of the world due to increased competition for soy and grain without increased supply.

It is, nevertheless, a reality that the diesel oil available as a fuel today is not the same as that available when our diesels were designed, or even when they were newly installed. Currently regulations vary in different parts of the world but road diesel in the UK is 7% bio-diesel and 93% petroleum diesel.

It is this fraction of your diesel that is prone to absorbing water. Boat owners face a unique set of challenges for storing diesel fuel – at least in comparison to car owners. Typically, cars use their diesel supplies quickly and store it in relative dryness. On boats, the diesel might be months or even years old and any air that enters the tank via the breather pipes will invariably be damp. Damp air in tanks will condense on the walls at night and run into the fuel. In the past, this would sit at the bottom of the tank until the tank was eventually cleaned out. Now, the water can be absorbed into the fuel and transported to the engine. Damp fuel can lead to moisture in the cylinder causing white smoke and corrosion in the engine head.

Bore Polishing in Diesel Engines

Think for a moment about the inside of a cylinder in a diesel engine. The inside cylinder wall needs to allow the piston to move up and down at great speed, forming a vacuum and a high pressure by turns. Although the piston is a tight fit in the cylinder, it must not allow the pressurised gases (or the fuel) to leak into the body of the engine and contaminate the lubricating oil. This is achieved by piston rings, which slide up and down between the piston head and the cylinder wall. We obviously want to lubricate the cylinder wall with oil to help the piston rings do their job.

When modern diesel engines are manufactured, the cylinder bores are honed (machined) to produce a “crosshatch” appearance with fine grooves from both directions at about 22 degrees from the horizontal (see below).

The crosshatch pattern is required to retain oil to ensure proper lubrication and to form a seal between the piston rings and cylinder bores. Bore polishing is characterized by a clearly defined area of bright mirror-like finish on the cylinder bore where the crosshatch pattern is worn away (see below).

Bore polishing is caused by a build-up of carbon deposits in the piston top ring land area, i.e. the part of the piston above the top ring. Poor combustion of diesel fuel leads to these hard carbon deposits, which are highly abrasive and scrape away the honing grooves on the cylinder bores. Bore polishing leads to increased oil consumption (blue exhaust smoke) and loss of combustion pressure and performance. This is because the oil film trapped in the honing grooves that maintains the piston ring seal and combustion pressure, is no longer there. Unburned fuel and combustion gases then leak past the piston rings and contaminate the lubricating oil.

There is evidence that operating older style diesel engines with modern high-spec synthetic and semi-synthetic oils, and also running them at constant revs for long periods of time (i.e. in the hours) without varying the throttle can caused bore polishing.

15W40 means that at cold temperatures the oil has the same viscosity as SAE 15W oil. At high temperatures it has the same viscosity as SAE 40 oil. The 15W40 designation means that the oil is a multigrade oil. It has the viscosity of 15W when cold and the viscosity of SAE 40 when hot. This means that one type of oil works in all temperatures. The Society of Automotive Engineers or SAE has established an arbitrary scale for the viscosity of motor oils. The scale ranges from 0 to 60. The numbers from 0 to 25 have the letter W added. This means that they are “winter” viscosity, for use at lower temperatures. The viscosity of a liquid is its resistance to flow. High intermolecular forces between the molecules cause a high viscosity. As the liquid warms up, the added kinetic energy overcomes some of the attractive forces. The viscosity decreases. Hot molasses flows more readily than cold molasses. A single grade oil like 15W or SAE 40 oil has a high viscosity when cold and a lower viscosity when hot. The first number 15W is the viscosity of the oil at cold temperature, and the second number 40 is the viscosity at 100 °C. The 15W40 designation means that the oil is a multi-grade oil. It has the viscosity of 15W when cold and the viscosity of SAE 40 when hot. This means that one type of oil works in a range of temperatures.

Thanks for visiting SaltWaterDiesels. This page isn’t quite ready for the water yet do but check back soon to see updates – we’re launching new articles all the time.

Marine Expert

8 Best Small Outboard Motors – (Reviews & Guide 2022)

Looking for the best small outboard motor out there? This piece of equipment is essential for most sailors out there, so picking a great model is important.

That’s why we prepared small outboard motor reviews to see which models have gathered a lot of appreciation on the part of the boaters that have invested in them. These are all capable of excellent performance and are also easy to maintain. You can also find our comprehensive buying guide where you can learn what exactly to look out for.

See The Quick Comparison Chart

Advantages of Small Outboard Motors

If you have been wondering whether this type of motor addresses your requirements or not, you’re going to enjoy reading the following section. We have put together a list of some of the most significant benefits that you will get if you decide to start using an outboard motor for your boat.

1. Easy to Replace

The first and most obvious advantage is that the engine can be replaced very easily in case of failure. An outboard motor is capable of improving a boat’s handling since it provides articulated thrust unlike rudders used with inboards. Most modern outboards are able to offer an excellent power-to-weight ratio, especially when put side by side with the other options out there.

2. Size and Space

Small outboard motors are easy to handle, lighter than their heftier counterparts, and they also occupy less space on your boat. Their name is ‘outboard’ for a reason, meaning that you can use the amount of space that they put at your disposal for anything else — a boat seat or use it as storage for something you might need while out on the water.

3. Maintenance & Dependability

A few years ago, diesel inboards would have been more likely to be yard-maintained by a professional mechanic, and therefore, they would have been pricier to own and use compared to outboards.

If you have to upgrade or replace an engine or prop, it’s far easier to do it with an outboard. Since everything is at your disposal, you can also take a good look and see whether the motor has sustained damage from an impact, for example.

Outboards run on gas whereas inboards are mostly diesel-powered. You can, of course, come across gas inboards, but for safety reasons, diesel ones are recommended. Diesel is about twenty percent more expensive than gasoline, so outboard motors make it cheaper for you to do your boating.

On top of everything, over the past decade, diesel motors have become less and less popular, also because they produce a lot more pollution. Some countries have forbidden diesel cars completely and are forcing their owners to upgrade to a gas automobile. At this point, we don’t know if this will happen with diesel motors for boats, but it’s quite likely that it will.

Small outboards motors that don’t come with any bells and whistles can be quite affordable. While the cost might not be the most important aspect to consider, it does make a difference, especially if you are on a budget.

However, there are expensive outboard motors, too, such computer-controlled models, many of which can be quite sophisticated.

Best Small Outboard Motors Comparison Chart

Best small outboard motor reviews, 1. sky 2-stroke 2.5hp superior engine outboard motor.

Furthermore, the 2-stroke single cylinder engine can get you moving on the water efficiently and easily, but also in as little time as possible. The 2.5HP motor makes the perfect choice for inflatable boats or small fishing boats.

Additionally, you might want to know that this engine comes with a compact and durable construction, which means that you will get as much use of it in the future as possible. Plus, it’s also easy to store and carry, which makes winterizing it a breeze. Last, but not least, we’d like to add that the motor doesn’t make as much noise as you might expect it to.

• Suitable for freshwater and saltwater
• Lightweight and easy to carry
• Doesn’t make a lot of noise
• Compact and durable
• Perfect for small inflatable boats
• This one isn’t powerful enough for bigger and heavier boats, so we would recommend against purchasing it if that’s the type of watercraft that you own.

2. Coleman Powersports 2.6 HP Outboard Motor

The easy start TCI ignition, the 360-degree steering, as well as the fact that this motor has been both CE and EPA approved are all things worth writing home about. It has been specifically engineered to offer reliable and quiet operation. That’s why it makes one of the best options out there for inflatable boats and small boats.

Needless to say, you are also free to rely on this outboard motor as an auxiliary trolling engine. On the other hand, it calls for a significant financial investment, so do keep that in mind when deciding between this one and another unit.

• Adjustable steering friction
• Vibration reduction
• Made with marine aluminum alloy parts for corrosion protection
• Meets EPA and CE standards
• It’s water-cooled, so operation is a breeze
• The fuel shutoff valve works backwards, which might confuse some boaters in the beginning.

3. US DELIVER Outboard Motor 6.5HP Water Cooling 4-Stroke

The 6-HP engine gives you all the power that you need. It runs on gas and it does tend to make a lot of noise, so you do need to consider that before investing your hard-earned cash in this one. The unit doesn’t wear more than 100kg, which makes it lighter than some of its competitors.

It is a great match for rubber boats, inflatable boats, but also some types of fishing boats. As for the fuel efficiency, we haven’t come across any complaints in this sense. We also couldn’t help noticing that most of the feedback acquired by this unit is favorable.

• Comes with a booklet, tubing, cotter pin, a start rope, a start key, and a pump impeller, but also a toolbox and other accessories
• Has been approved for use by the CE
• Max speed (r/min) is estimated at 5000-6000
• Very powerful, given its 6.5-HP
• Newly designed handles make it easy to transport
• It’s not the cheapest engine in this line.

4. CLIENSY 4HP 4 Stroke Outboard Motor Boat Engine

The engine is equipped with its own patented air cooling system, which means that you can rely on it for a whole day of fishing. Furthermore, it comes with a 360-degree steering rotation for reverse without any gear shifting, so you also get to operate it conveniently and easily.

If you are worried about durability and safety, you will be happy to know that this unit comes with a lubricating system and a safe twist grip throttle control. This engine makes an excellent alternative for fishing boats, inflatable boats, as well as rubber boats.

• Can be used in freshwater and saltwater
• Weighs in at just 29lbs
• It’s a dry motor, so it uses air cooling, not water cooling
• Very easy to grease and get ready for the winter
• Fairly inexpensive
• This unit wouldn’t be strong enough to pull a raft or to be used for water skiing.

5. NOPTEG Hangkai Water Cooled 2 Stroke 3.5 HP Outboard Boat Motor

You can’t compare a 6.5HP engine with a 3.5HP one, but you can definitely opt for this one if your boat is light and you don’t need a lot of power. The cooling technology is another aspect to keep in mind, and this one is water-cooled, which is convenient and reliable.

On top of everything, the NOPTEG alternative is eco-friendly, energy-efficient, and also easy to carry. The compact design makes it easy for you to service your engine before you store it for the winter. You don’t have to worry about anything in terms of durability as this one is made from high-grade marine material, so it doesn’t corrode easily.

• Perfect for fishing boats, inflatable boats, but also small yachts
• Covered by a 1-year warranty
• It weighs in at about 21 lbs, so it’s quite lightweight
• Durable and easy to operate
• It can smell like rubber when it’s running, which can bother some boaters.

6. SEA DOG WATER SPORTS 4 Stroke 4.0HP Outboard Motor

As for the waters in which you can rely on this motor, you’ll be glad to know that it works both in saltwater and in freshwater. It can be installed on a variety of watercraft from fishing boats, canoes, and sailboats to good old kayaks.

Durability is not a factor that you should worry about if you decide to opt for this model. It boasts a compact structure, but it is made to be anti-corrosive, meaning that it’s not going to become the victim of rust anytime soon. It’s also quite lightweight and easy to carry around.

• Modern fuel-saving technology
• Can be installed on a broad range of ships
• No assembly required
• It starts easily, with almost no effort and no issues whatsoever
• Backed by a 1-year warranty
• It calls for a financial investment compared to other small and budget-friendly choices in the same line, but we might argue that it pays off in the end.

7. SEA DOG WATER SPORTS Outboard Motor 2.5 HP 2 Stroke

Nevertheless, it still makes a great option for watercrafts such as small yachts, fishing boats, inflatable boats, as well as sailboats. It’s durable, economical, and compact, so you can service it with as little effort as possible. What’s also worth noting about it is that it boasts an anti-corrosive construction.

Being compatible with both freshwater and saltwater, you can basically use this engine anywhere you please or wherever you do your boating or fishing. It’s a single-cylinder, 2-stroke, air-cooled model and it works with less noise, especially compared to others. As a final note, this model works with gasoline, so do keep that in mind when making your decision.

• Works great based on the feedback it has received
• Offers excellent power for a small boat
• Offers amazing value for every cent spent
• The motor can be tilted
• More stable and reliable compared to traditional land motors
• Since it’s been described as a weed eater, try to avoid using it in waters with heavy cover.

8. HANGKAI 6HP 2 Stroke Outboard Motor with Water Cooling System

It’s also worth noting that it comes with 360-degree steering rotation for reverse without any gear shifting whatsoever. You might want to consider this unit if you are in the market for a convenient and easy-to-operate engine that’s also fuel-efficient and eco-friendly.

Despite its quite large tank capacity, the motor boasts a compact design. This is one of the reasons that makes it easy to winterize and carry from one place to another and even install on another boat, if you’re looking to change your watercraft. As is the case with some of the other engines described in this selection, this one is CE certified.

• Suitable for freshwater and saltwater alike
• Works on a variety of ships
• Comes with a 2.5L fuel tank capacity
• Doesn’t take a lot of skills and effort to operate
• Convenient, reliable, and reasonably quiet
• Avoid starting the motor on the shore or using it when you come out of the water — this can result in irreparable damage.

What is an Outboard Motor?

Similarly to many other marine power systems, the engine spins a shaft. The shaft consequently spins a propeller shaft, and the latter spins a propeller so as to create thrust.

If you have been trying to tell whether alongside the rest of your boating gear , you should consider using an outboard motor, we’re here to help you understand just that. An outboard motor simplifies the boat building process as both an inboard or stern drive would have to be mounted to the motor, lined up, and then attached to the drive system.

Like other types of equipment, from the models from our boat seat reviews to boat anchor reviews , outboard motors have come a long way in the past years. They were invented at the end of the 19th century and they initially were 1.5-horsepower motors that could be clamped to the back of any rowboat. Later on, 2-stroke and 4-stroke motors were invented.

Different Types of Outboard Motors

1. Two-Stroke Outboards

If you are both price and weight conscious, what you need is a two-stroke small outboard motor. It effectively produces the compression strokes of the plunger and its consumption in just a single action.

Two-stroke outboards are usually lighter, cheaper, and they also have a simpler construction compared to their four-stroke counterparts. This is what makes them easy to maintain. They are also quite rugged, in spite of their size and somewhat ‘limited’ capacity.

2. Four Stroke Outboards

4-stroke engines have become more and more popular in recent years, and that’s because they use less fuel, they are quiet, and they also tend to run more cleanly. There is no oil mixed with the fuel, so the two-cycle smokescreen is automatically eliminated.

Four-stroke outboards also have a greater economy and fewer emissions, so if you’re not so particular about the size (since they tend to be bigger and heavier), you might want to consider this type.

The weight is something definitely not worth writing home about when it comes to four-stroke outboards. For instance, four-stroke engines that are in the 5-HP category are about 20% heavier than 2-stroke engines that have the same horsepower. They also tend to cost a pretty penny compared to their 2-stroke counterparts.

The nice thing about four-stroke outboard motors, though, is that they are in compliance with environmental regulations. This, of course, can’t be said about 2-stroke motors.

3. Cooling Categories

Every engine, no matter whether it is small or large, or four-stroke or two-stroke, will have to be cooled using one method or the other. To date, manufacturers have come up with two types of cooling:

• Air cooling
• Water cooling

Air-cooled systems cool down the engine thanks to a fan. They are quite rare, they’re small, and they don’t seem to do that good of a job.

Water-cooled systems , on the other hand, are a great choice in most situations. They obviously rely on water to cool the motor. Most compact outboard motors rely on closed-loop cooling where the surrounding water is used for the purpose. However, the water never gets into the motor or the boat.

Small Outboard Motor Buying Guide

It contains all of the essential aspects that you ought to mull over before you make up your mind on a specific model. Check it out below.

1. Horsepower

This factor is by far the most important one to consider when shopping for a boat motor. Technically, bigger is better, but the truth is that you have to pick the right horsepower for the boat type and size that you own. If you have a small boat and you get a large engine, it might affect the ship’s stability. Plus, the additional power can cause damage to the transom.

On the other hand, using a too small outboard motor on a boat that’s too large can effectively burn out the engine due to excessive demand and drag. Making sure that the size and horsepower of the motor match your boat can provide you with reliability, but also stability.

There is an easy way of telling what type of HP motor you should get. You can look at the National Marine Manufacturers’ Association Certification Plate, which should normally be found inside your boat stern. There you will find the horsepower rating that is recommended for your type of ship.

2. Transom Height

The boat transom is the part of the backend where you will mount your portable outboard motor. The reason this part is so important is that the thrust and momentum of the engine will be transferred to the whole boat through the transom.

Look at the transom height when shopping for any outboard motor as you need to make sure that it is a good fit for your type of vessel. You can measure the transom height of your boat by measuring from the top center section to the bottom center of your hull.

3. Electric Start

Recoil start engines can be difficult now and then, but today’s recoil start motors are easier to work with thanks to their automatic decompression. This feature effectively bleeds off cylinder pressure so as to reduce the pulling force.

There are outboard motors out there that have an electric start. The core advantage of an electric start is that it can get the engine running with just one push of a button. It can also give you some reassurance when it comes to safety. If you end up in a rocky shore area, you can just press the electric start button and get away from danger.

4. Fuel Type

Gasoline can be a little more expensive and it can also put less strain on the engine valve seats, especially when compared to propane. It has been the fuel of choice for many years now, and many boaters will find it comfortable to work with.

However, propane has been gathering a lot of appreciation, too, and that’s because it’s more efficient and also cleaner than gasoline. It will also not gum up or degrade the engine as fast. In addition to this, propane engines start quicker and more easily as the fuel is effectively pressurized.

If you already use propane as a fuel for other types of equipment, such as your grill, for instance, you might want to eliminate gasoline altogether and choose a motor that can be used with propane. You might want to do this out of pure convenience.

5. Controls

For manual tilting, you should find a tiller handle that you can just push down and snap from and into any angle. Most portable outboard motors come with a power tilt and this can be a great feature to have, but it can be difficult to work with on larger engines.

After launching your ship, you will have to tilt it down into the water, so you might need to tilt your motor up, especially in shallow areas. You’ll need to tilt it back down when you get back to deeper waters. You should also tilt up your outboard motor when you are retrieving your boat at the boat launch.

There are modern outboard motors out there that are built with EFI engines. These ensure controlled throttle response and reliable and fast starting no matter the weather. On top of everything, EFI engines are known for not gumming up like carburetor engines. They also call for a lot less maintenance in the long run.

Although the vast majority of boaters seem to prefer the simplicity of carburetor engines, many will learn to appreciate how efficiently and clean EFI models can run, even in inclement weather or when it’s very cold outdoors.

7. Size & Weight

The size can matter a lot in the grand scheme of things. If the engine is too sizable for your ship, it can make the latter lose its balance. This can mean that you and the rest of the people in the boat can be put in a dangerous situation.

Picking the right size of motor can be done easily nowadays since most manufacturing companies can be contacted and they can give recommendations with regard to which engine size works best for what ship size.

As for the weight, it also has a say in your decision. If the motor is too heavy, it might not work properly, and it might also make the front of your watercraft lift up and essentially modify its position on the water. Under such a circumstance, a boat can lose power and speed, which has a negative impact on fuel efficiency, too.

As we have already mentioned, the majority of small outboard motors that are available for sale right now are either two-stroke or four-stroke. If fuel economy and being environmentally friendly matter a lot to you, a four-stroke engine is the best choice of the two.

On the other hand, two-stroke engines are smaller, have a simpler construction, and they also tend to cost significantly less compared to their four-stroke counterparts.

9. Shaft Length

All outboard motors come with a shaft, and it can be either short or long. If you have a lower boat, then you should definitely select a motor that comes with a shorter shaft length.

On the other hand, higher boats call for longer shafts. The length of the shaft goes a long way when it comes to determining the performance and cooling system of the motor.

10. Build Quality

You can’t really assess the construction quality of a small outboard motor just by having a look at some pictures online. Make sure you read as many reviews of the outboard motor as possible before ordering it. Additionally, we would like to note that in this case, the brand actually matters.

It is universally acknowledged that bigger brands make their products using better quality materials. Plus, if you get a model made by a reputable company, you will also benefit from a generous return and refund policy in case you come across any problem.

How to Install & Use a Lightweight Outboard Motor

General Tips

• Make sure that the engine is in the correct position.
• Tighten it and look at how you can use it in relation to your hand or other type of operation. The middle part of the outboard should be moved up and down with as much ease and convenience as possible.
• Check the manufacturing brand’s manual and then look at the pictures provided and compare them with the reality. If the motor doesn’t seem to be well-installed, call a technician.
• Before using the motor for the first time, make sure that it is fastened as best as possible so that it doesn’t detach from the boat when being operated.
• Rely on safety cables to position the motor as best as possible. This will ensure that, in the unlikely event that the motor bumps into an object in the water, it won’t be knocked down from the transom.
• Position the outboard motor’s fuel tank in a well-ventilated area of the boat. Ideally, this part of the boat should also be away from direct sunlight and no more than six feet away from the outboard motor (and less than 3 feet below the fuel connector).
• Always use a startup checklist before anything.

Maintenance & Safety Tips for Portable Outboard Motors

It can be more or less easy to keep your outboard engine in top shape, even if you aren’t a mechanic. A little TLC and preventive maintenance can make sure that your boating is always safe. It can also make sure that the motor runs reliably for many years to come.

Regular Maintenance

Prevention is worth a pound of cure, they say, and we couldn’t agree more. Here is a checklist of things that you ought to ensure on a regular basis.

• Check the fuel line for worn spots and cracks.
• Make sure that the fuel primer bulb isn’t cracked or pliable.
• Ensure that the fuel line fittings don’t leak and seat right.
• Check the clamps for corrosion or rust, especially those on the fuel line.
• Check the fuel tank for corrosion or any other type of damage.
• Check the tank vent so as to ensure that it aspirates correctly.
• Regularly check for any water present in the fuel.

After Every Trip

1. Flush Out the Motor

Remove the water using a hose connected to the water outlet and then run the engine until there’s no more exiting the hose.

2. Burn Off Any Excess Fuel

Turn off the fuel tap and run the engine until it naturally stops. This will get rid of the fuel in the carburetion system. Needless to say, make sure that the battery switch is turned off when the motor isn’t in use.

3. Check for Leaks

Remove the engine cowling and inspect it for fuel or water leaks. If you find one, get in touch with your local mechanic as he or she can perform repairs before things get worse. Pipe clips can also become loose quite easily, and if you notice any signs of rust or corrosion, you should change that clip.

4. Use WD40

Spraying the engine with WD40 can protect it against corrosion. After getting rid of any rust present on the motor parts, you should use an appropriate lubricant. As time-consuming as these tasks might seem, they are essential in maintaining your outboard for as long as possible and in as good condition as ever.

5. Fresh Fuel

When the season ends, drain the fuel from the tank. It goes without saying that you should dispose of it correctly. Grease everything before storing your boat and get in touch with a mechanic so as to perform a thorough check of your motor. The same should be done when the season starts, again.

FAQs About Small Outboard Motors

1. how to winterize an outboard motor.

Winterizing an outboard involves several steps. First, fill up the gas tank, which gets rid of the moisture buildup over the winter months. Check the bulbs, hoses, and connectors and replace them if there is any damage present. Change the water separator and fuel filter and add a fuel stabilizer to the gas tank — this makes sure that the gas is fresh in the spring.

Use a motor flusher and while the water’s running, start the motor and allow it to go idle for a quarter of an hour. Spray a fogging agent through the carburetors until you see smoke coming out the exhaust and the engine kills. The oil lowers the chance of any moisture occurring inside the motor.

Spin the flywheel by hand several times to distribute the oil as evenly as possible. Check the spark plugs for wear. Coat the engine body with silicone anti-corrosion spray as this will prevent moisture from sticking to its parts.

Remove the propeller and inspect for weeds or fishing line or whatever else that might have become entangled around the shaft. If the seals are obviously damaged, they have to be replaced. Then coat the shaft with lube and replace the prop. You have now winterized your outboard motor.

2. Where Should Water Come Out On an Outboard Motor?

Water should be removed via the hose attached to the water pump. However, there can be situations in which you might notice that water is coming out of your exhaust pipe, for example.

You should know that cooling water can exit through the exhaust and it’s absolutely normal. It’s a part of the cooling system, along with the pee stream. When you are not moving, the exhaust can even bubble out from the lower unit as it exits out through the prop while you are underway. There’s nothing to worry about, in this case.

3. How to Build an Outboard Motor Stand?

Building a motor stand really isn’t that difficult. You do have to make sure that it is a good fit for the engine that you have on your hands, though. For example, for a 550lb engine, you’d need bottom runners that would have to be 4×4 3’, 2 feet behind and 1 in the front, and a height notched 1” into the bottom runners.

You’d also need a 12-motor mounting plate, 2×4 side support and one behind the upper legs, and 3/4″ side plates. You can use glue, screws, and lags, and even add casters later on. There are a lot of free instructions on the Internet, as well as tutorials and tips.

As you might have been able to tell, picking the best small outboard motor from the plethora of the models that are available these days can be quite challenging. We hope that our small outboard motor reviews have assisted you in making the right decision for your boat and your needs and preferences.

Just remember to do as much research as possible before opting for one unit or the other. Go through as many consumer reports as your time allows you to as other boaters can let you know what mishaps they have encountered, especially in terms of installation, operation, and maintenance.

About Peter Richardson

Peter Richardson decided that he needs to balance out the sedentary lifestyle of a software developer by getting out there more. He found passion in none other than – boats. This website represents everything he learned along the way. Finding the right equipment for your boat is no easy task, and that is what Peter’s articles aim to help you with.

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The Best Outboard Motor for a Sailboat

Last Updated by

Daniel Wade

June 15, 2022

The technology of sailing has remained mostly unchanged for centuries. Since learning to harness the power of wind, sailors have been transiting the world’s oceans, expanding trade routes and exploring new cultures. Although nothing more than a renewable natural resource and a single sail is needed to move a sailboat along the water, there are times when it’s important (and in our modern age, convenient) to leverage off a motor to get you where you need to go.

Like any unique piece of equipment in the world of sailing, outboard motors come in a variety of sizes with features and options to fit any owner’s needs. But of course, one size doesn’t fit all. Every boat is different – even those that come off the production line at the same time – and every owner is looking for something specific when it comes to their sailboat. From the purpose of owning the boat (blue water sailing vs. racing) to the location and impact on maintenance (cold weather vs. tropical weather), an outboard motor is just one of the many elements that will define a sailboat’s function and performance.

Whether you’re a new owner, or a veteran sailor, it’s important to know the basic components of any outboard motor . You should also have an idea of what you want your outboard motor to do for your size and model sailboat.

Table of contents

Outboard Motor Size

A larger boat doesn’t necessarily mean a larger motor. Although there are different ratings for different classes of boats, a small power plant can be more effective than a larger one. Conversely, an outboard motor can easily overpower a small boat and create unsafe conditions at high speeds. Guidelines and requirements differ between motorboats and sailboats. And while there is some overlap, these considerations apply directly to sailboats.

Engine power has to do with how much water a boat displaces. For sailboats, smaller is better. If you’re a bit of a math geek, the exact formula is 4 horsepower for every 2200lb of weight. Coupled with a propeller size, which can be determined using a propeller calculator , you’ll get a rough estimate to use as a guideline to start shopping. This is a good first step, since size is essentially a fixed variable. Though it’s worth noting for those who are buying a sailboat directly from the manufacturer, that actual weight will increase after delivery – once all other rigging and outfitting has been completed.

Physical size of your outboard motor is an important consideration and is directly related to the design of your sailboat. An outboard motor is made up of three parts from top to bottom:

• The Powerhead – Houses the engine. The bulbous part of the motor.
• The Midsection – Houses the exhaust system. Varies in length and design.
• The Lower Unit – Propellers attach to the gearbox. Submerged when operational.

Shaft length is an important design element and should be considered when purchasing a motor. A shaft that is too short will obviously prevent the propeller from being submerged in water, while a shaft that is too long will extend the propellers too far. Not only will it decrease the efficiency of your engine, it will create unnecessary drag. Know your transom length when looking at different models.

When an outboard motor is not being used, it should be stowed in its upright position. Some of the larger motors have an automated switch that will raise it out of the water, but some must be secured manually. Make sure everyone who sails with you is capable of lifting and securing the motor out of the water in case of an emergency.

Outboard Motor Power

Any kind of motor installed on a sailboat (inboard or outboard) should be viewed as a tool to help with maneuvering. Although there are some very skilled sailors out there who can sail into their slip without the aid of a motor, many harbors have restrictions that either don’t allow for the use of full sails, or there simply isn’t enough room to maneuver. A motor with both forward and reverse gears helps tremendously with docking.

While there is no exact correlation between boat length and total weight, the following is a rough guideline:

• 1-4 HP for boats up to 20’ (approximately 1000-2000lbs)
• 4-18 HP for boats between 20-30’ (approximately 2,000-10,000lbs)
• 18-34 HP for boats between 30-40’ (10,000lbs or more)

There are some things to consider when deciding how much horsepower you need or want. Location and the type of conditions you expect you’ll be sailing in is one of the biggest factors. Heavy seas and high winds typically associated with open ocean sailing will put more strain on your engine, and in some cases overpower it, whereas an engine that is heavier than needed will add unnecessary weight when racing. If you plan on motoring for long distances, consider purchasing an engine that will stand up to a lot of use.

Less HP is required for:

• Boat Design – Single hull boats made out of fiberglass require less power.
• 2-Stroke Engines – This is due to an overall lighter weight engine and higher torque.
• Diesel Engines – Diesel delivers more torque because the rate of compression is greater.
• Bigger Propellers – More surface area means more water displacement.
• Location – Motoring on lakes and rivers requires less power than open ocean.
• Distance – A smaller engine is suitable for shorter distances.

More HP is required for:

• Boat Design – Catamarans and heavier boats (regardless of size) require more power.
• 4-Stroke Engine – Engine weight and an extra step of compression yields less power.
• Gas Engines – The rate of compression for gas engines is much lower than diesel.
• Smaller Propeller – A smaller propeller displaces less water.
• Location – Open ocean, with tides and currents, will strain a smaller engine.
• Distance – Cover more distance when wind conditions are poor requires a larger engine.

Outboard Motor Cost

There is no way to quantify how much you will pay for any given motor. But there are several costs associated with owning an outboard motor that are definitely worth considering when making your purchase.

Certainly, a lager, more-powerful engine is going to be costlier than a smaller engine with lower horsepower. But as mentioned earlier, size is not necessarily a guarantee of performance and efficiency. At the same time, there’s only so much you can get out of an engine before you exceed its capability. Larger engines tend to help with resale value should you choose to sell your boat at some point, but a boat outfitted with right motor to begin with will always perform better than a motor that’s large just for the sake of it.

Factor in maintenance costs and fuel when looking at models. You want to run your engine at around 90% of its max RPMs to balance proper fuel usage and with wear and tear. Making a few calls to marine mechanics to inquire about an engine you’re interested in will give you a lot of information a sales person won’t be able to give you. The good news about outboard motors is that most of them are portable, which means you won’t have the added cost of either paying a mechanic to come to you, or having to get your boat to the yard, which usually requires help from a very good friend willing to spend all day driving and sailing back and forth.

Owning a boat requires constant care and maintenance, so a little knowledge goes a long way. While an outboard motor is not required for sailing, it’s a convenient addition that can greatly increase your enjoyment out on the water. Being patient and spending time researching engines will not only help you make the correct purchase but will help you take advantage of a great deal when it presents itself. Whether you sail the Caribbean, or race off the coast of California in a catamaran, there is an outboard motor that’s just right for you.

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I've personally had thousands of questions about sailing and sailboats over the years. As I learn and experience sailing, and the community, I share the answers that work and make sense to me, here on Life of Sailing.

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Best Small Outboard Motors: A Comprehensive Buying Guide

Small outboard motors are perfect propulsion solutions for small boats, including dinghies, tenders, canoes, kayaks, skiffs, and Jon boats.

However, mind that small outboard motors are not trolling motors that only provide limited power and range (Check our previous post comparing outboard motors vs trolling motors ).

A reliable small outboard motor should be lightweight and quiet, yet powerful enough to get you from point A to point B effortlessly, even when dealing with tides or swift rivers.

Having searched around and found yourself overwhelmed by nearly endless options of small boat motors with mixed reviews? Making it even ‘worse’, now you have affordable options of small electric outboards.

No worries. In this post, we will have a detailed comparison between portable electric boat motors, small gas outboards, and other options available (such as trolling motors), with the best recommendations to help you make a quick decision.

Table of content:

• Electric vs. Gasoline
• Best Small Boat Motors

Small Outboard Motor: Electric vs. Gasoline

Here we list the top 5 reasons and occasions you should consider an electric outboard vs. a gas small boat engine.

‘I’m searching for the quietest small outboard possible.’  A quiet ride is one of the benefits of small outboard motors compared with those big engines.

If you want to cruise silently up and down the river, the best solution is to go electric. The electric small outboards are surprisingly quiet because they don’t rely on the internal combustion which causes loud noise and vibiration.

Thanks to the industry leading direct drive technology and FOC (Field-Oriented Control) built into the small outboard motors, ePropulsion outboards further reduce the number of internal moving parts and eliminates the gearbox, making the quietness a next level. You will simply hear no noise but the sound of nature.

Here is a video comparison between small gas boat motors and their electric counterparts:

Key takeaway:  If quietness is your top priority, small electric outboards will be your best choice. You will feel the difference immediately once you switch over to electric motors.

#2. Lightweight

Portability is another crucial factor for users to choose small boat engines. Usually, the small portable outboards can be hand-lifted easily, making them easy to transport, attach and remove from your boat. The weight for gas and electric small outboards is neck and neck, generally ranging from 9 kg – 10 kg for a 3 HP outboard motor.

However, don’t forget to include the weight of gasoline required (for small gas outboard motors) and the battery pack (for electric motors). The electric small boat motors usually come with built-in batteries for easy installation and transportation, making it a more portable solution.

#3. Power & Range

The power is a big drawback for some lightest (or cheap) small outboard motors. With those smallest boat motors, such as trolling motors rated by thrust, users might have difficulty moving forward when caught in the gale or tide, even at its max speed.

If you need more power to help you feel safer on water, you need to consider some higher-powered small outboards, and 2.5 or 3 hp small outboards can be a good starting point to deal with the possible elements on water. 

For example, the 3 HP small outboard  ePropulsion Spirit 1.0 Plus  gives you  4.5 mph  speed,  5 hours  runtime and  22 miles  range with a single charge of its  1276 Wh  battery (tested on a 12-foot aluminum boat with one person on board in calm water). 

#4. Easy to Use & Maintain

Forget about the ignition and pulling the cord every time to start the small gasoline outboard motor. With electric boat motors, you only need to press one button and you are ready to go. It’s simple to use for all your family members.

Electric outboard motors are made for a premium experience. It’s easy to operate with the built-in tiller handle, and you will stay informed of the real-time battery status with its convenient digital display. So no worries about getting stuck in the middle of a lake.

Some small boat motors featuring direct drive technology are maintenance-free, saving you a lot of trouble and money in the motor service.

The price might be a big reason that puts off your decision on buying a electric small outboard motor. Some of you might be looking for small boat motors for sale or cheap small boat motors resellers on the market.

It’s true that the initial investment is higher than the petrol counterpart, but you will be compensated by the savings on petrol cost, maintenance fees, and the superium experience it provides. You will be surprised that you will start to save within a few years of use (about 150 hours of service time), according to our calculation .

If you want to save some budget on the small outboard motors, you can pay attention to online and offline activities to get some hot deals and save money. For example, you can get a discounted ePropulsion small outboard motor by becoming our  pro staff .

Best Small Boat Motors: Top 2 Options

As we have discussed above, electric small outboard motors can be your ideal solution for small vessels in terms of the motor weight, power, range, and cost in the long run.

So what’s the best option for a reliable small outboard? Does anyone have a brand they suggest?

Check out the top two electric small outboard motors models recommended by industry professional reviewers and customers from over 40 countries.

#1. Spirit 1.0 Plus: 3 HP

As one of the most popular selling models, Spirit 1.0 Plus has everything you may expect from a small outboard motor, plus extended battery life and long range.

Designed for dinghies, fishing boats, and sailboats, Spirit 1.0 Plus is suitable for various applications, providing you with enough power to go fishing all day long at trolling speed.

Performance:

Features you will love:

• Quiet, no noise to disturb your journey
• Clean power, environmentally friendly
• Portable, easy to install and transport
• Easy to use, all family members can enjoy the fun
• Digital display, real-time access to battery status
• Integrated floating battery
• Solar charging supported
• Free of maintenance, saving cost and trouble

Customer Reviews:

‘Tried our spirit 1.0 plus for the first time today on our old tender dinghy and the difference between that and the old gas motor is amazing. Not just noise and smell. But performance too.’

The above comment is quoted from Miles Buckhurst’s sharing on ePropulsion Owners Group. Here is also a video that compares ePropulsion small outboard motors with other alternatives (trolling motors and more). Check it out for details:

In addition, ePropulsion offers three years warranty upon  product registration . So you are covered if anything happens to your ePropulsion small outboard motor.

#2. Spirit 1.0 Evo: 3 HP

Spirit 1.0 Evo has inherited all the benefits from the Plus model and innovatively been integrated with the extra hydro generation function.

It allows the battery to be charged while sailing. If you are looking for a small outboard motor for your sailboat, Spirit 1.0 Evo would be a better fit.

For the hydro generation charging capacity and more genuine comments, you may check out the below review video from  The Sailing Frenchman:

If you still need more battery capacity for a longer trip, you can check out ePropulsion E-Series batteries that provide extended runtime at an affordable price.

Small outboard motors bring a lot of convenience and premium experience to your boating activities. Whether you plan to use it for roaming around the small shallow river near your place, or want to go long ways and come back to the start points upriver and against the current, you would be happy and safe with a reliable small outboard motor.

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Selecting the perfect jon boat engine for your small boat requires determining what power you desire when moving through wind-driven waves. Your skiff, dinghy or jon boat requires an outboard that’s lightweight and quiet, yet powerful enough to get you from point A to point B. Selecting an 8 - 20 hp kicker motor will give you enough power to propel your small boat, while adding fuel efficiency at the same time.

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The harbor is like glass as you board the tender to your cuddy for a day on the water; your trusty Yamaha Portable ushering you out. With easy starts, incredible efficiency and reliable performance, Yamaha’s F6, F4 and F2.5, are perfect for all sorts of light duty. Wherever the day takes you, take along a little extra power with Yamaha’s smallest Portables.

Meet the Lineup

Our 139-cc 6-hp portable is an impressive little outboard. It boasts surprising features for such a small motor, like labyrinth exhaust and a long span mounting system for smooth, quiet power. It also offers the convenience of an external fuel tank (in addition to its built-in tank) for extended range and added convenience.

• Only 60 pounds (15” shaft model)
• Available in 15” and 20” shaft lengths
• Solid 6-amp alternator (optional)

Our 139-cc 4-hp portable outboard mirrors our OHV F6, with a couple less horses. It features the same ergonomic, easy-grip starter handle with a built-in decompression device for effortless starts. The F4 also features a built-in fuel tank with the option of switchable access to an additional external tank for amazing extended range. There’s no stopping this little brute.

• Solid 6-amp alternator

Our 72-cc 2.5-hp portable outboard is the smallest motor on our roster, but it still packs a punch. Completely redesigned, it’s even more portable, easier to store and clean burning.

• Only 37 pounds (15” shaft model)

† Weight refers to shortest shaft length, and is measured without motor oil, gearcase oil and propeller (except models 25 hp and under, which include a standard propeller). All Jet model weights include the jet pump assembly (weight estimated).

Compatible Controls

Compatible gauges, prop selector.

Enter your details. Find the right prop. Easily zero-in on the best propeller options based on your type of craft, horsepower and performance goals with this smart, online tool.

PORTABLES PACKED WITH

Performance.

They weigh as little as 37 pounds, but all offer impressive features like electronic ignition, thermostatic cooling and 180-degree steering.

Features & Benefits

They may weigh as little as 37 pounds, but these Overhead-Valve portable outboards are packed with features that create smooth, quiet power. This includes a CDI or TCI ignition system, an optimally balanced crankshaft, a long span mounting system and a labyrinth exhaust. 

The portable F6, F4 and F2.5 all offer impressive features like electronic ignition, thermostatic cooling and 180-degree steering.

Small motors use less fuel, but according to the Guinness Book of World Records, the Yamaha F4 actually set a world record for fuel efficiency, traveling 67.27 continuous statute miles on one gallon of gas.  

Yamaha’s F2.5, F4, and F6 feature our Easy Storage Oil Retention System. This pressurized oiling system prevents leaks, enabling on-side storage.  

Incredibly nimble, the F6 and F4 feature 180-degree steering and the F2.5 features 360-degree steering with a dynamically balanced and dampened twist-grip throttle for comfort and convenient maneuverabilty. 

Built-in front and rear handles make these lightweights easy to carry. Resting pads and an easy oil retention system allow for convenient on-side storage without cowling scuffs or oil leakage. 

RELIABILITY & DURABILITY

A pressurized oil delivery system that incorporates a compact and durable oil pump to keep all of the moving parts of their Overhead Valve systems lubricated and running smoothly for maximum reliability.

The F6, F4 and F2.5 feature built-in, see through fuel tanks. The F6 and F4 also feature switchable access to an optional, 3.1-gallon external fuel tank for extended range.

Combined with our proprietary alloy (YDC-30), our exclusive Phaze Five™ electro-deposited, anti-corrosive paint system provides a tough, five-layer barrier against corrosion. This protection is standard on all Yamaha Portable outboards.

The F6, F4 and F2.5 have a carburetor with a factory-selected setting for maximum efficiency. Additionally, automatic decompression, built-in auxiliary priming and start-in-gear prevention help make for easier starts.

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Yamaha's Got a New 7600-RPM, 200-HP Four-Cylinder Engine

We'll take our new engine debuts where we can get them these days. Even if they're in boats.

But the marine industry is a different story, and in recent years some of the coolest new engines— Mercury's V-12 , Honda's V-8 —were designed for boats. Which is also the case for Yamaha's new 1.9-liter four-cylinder, which makes 200 hp at 7600 rpm and can be found powering high-output WaveRunners and jet-drive boats. It's not designed for cars, but the Lemons racers among us can dare to dream.

The 1.9-liter four replaces Yamaha's 180-hp 1.8-liter mill and blurs the performance line between the company's naturally aspirated and supercharged engines. Yamaha's supercharged 1.8-liter makes 255 horsepower, but in a WaveRunner there's not a huge practical difference between the boosted 1.8 in a SVHO model and the naturally aspirated 1.9 that powers HOs. Personal-watercraft manufacturers adhere to an agreement that's something like the old German pact to limit top speeds to 155 mph, except on the water the target is 65 mph. That spec includes a 2-mph fudge factor, which naturally means that PWCs of sufficient horsepower top out at an electronically limited 67 mph. Since a 200-hp WaveRunner can hit that limit, the only difference is how quick you get there.

The 1.9-liter, as a new design, enjoys a bundle of changes aimed at durability and refinement. One example: There's an extra bolt connecting the cam chain housing to the block—a little tweak that makes a big difference. "The cam chain room is a thin aluminum casting," says Mark Sagers, senior watercraft factory service technical specialist (in other words, the guy who knows all the engines inside out). "That great big straight piece of aluminum is like a sound board, amplifying the noise of the cam chain. But if you run a fastener from that to the main casting, it knocks that noise way down. That's important when you're sitting right on top of the engine and it's bolted to a guitar body, basically."

Performance-enhancing upgrades include a new exhaust manifold with dedicated pipes for cylinders one and four, a bore increase from 86 mm to 88 mm, and a channel to route cooling water between the exhaust valves to cool the valve seats. The 1.9 even uses about a half-quart less oil than the 1.8, because Yamaha determined that it could cut windage losses (read: increase horsepower) without sacrificing durability. And durability versus performance is always a tradeoff, whether on land or not. "In a 250-cc motocross bike, the maintenance schedule calls for a new piston every nine hours and it's putting out specific power like a NASCAR engine, or almost Indy," says Sagers. "Boats are more on the lower end of high performance, so we can make them last thousands of hours."

A car engine might well make its horsepower peak beyond 7000 rpm, but it isn't expected to spend much time there. An engine destined for a WaveRunner is a different story. "A lot of the durability testing is done fully loaded at wide open throttle," Sagers says. "These will run a very long time at WOT. Waverunners are often idling or WOT, and there's no middle ground. But I've seen Waverunner engines with more than 1500 hours and no major mechanical work. It's staggering that these mechanical things can live through this."

Still, 200 hp isn't enough for everyone. Logically, it would seem inevitable that this engine will get a supercharger and the 1.8-liter will be retired. Boost prognosticators might find a clue at the 1.9-liter's Coast Guard–mandated intake flame arrester—the intake manifold is cast around it so it can't be sucked into the engine. Which is the kind of thing that would probably only happen if said intake was huffing some major boost. Perhaps soon, it will be.

In the meantime, you can break the 200-hp barrier without forced induction. And for twin-engine boats, that means Yamaha is packing 400 horsepower into some of its 22-footers, which we imagine would mean 50-plus-mph top speeds given that the 210 FSH hit 48.0 mph with the 1.8s and their 360 total horsepower.

Yamaha has built some nice automotive engines—most famously, the Ford Taurus SHO's —but those of us dreaming of 200-hp Yamaha-powered Miatas will probably have to wait a while for these latest ones to hit the salvage yards. (You can spend that interim figuring out how to adapt a closed-loop cooling system, since the jet drive on these engines doubles as a water pump.)

Calling a powerplant a "boat motor" is traditionally a pejorative, meaning a low-revving hunk of iron, an outdated castoff better suited as a mooring. But motors are electric, and that's where things are heading on the highways. So if you appreciate the mechanical complexity and cleverness of engines, boats are the new—and maybe last—frontier.

Ezra Dyer is a Car and Driver senior editor and columnist. He's now based in North Carolina but still remembers how to turn right. He owns a 2009 GEM e4 and once drove 206 mph. Those facts are mutually exclusive.

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Small Engines

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