Dinghy outboard motors

Doing your own maintenance! (Part 1)
Your dinghy’s outboard motor deserves as much attention and care as the main engines aboard your multihull: transferring crew in an anchorage or discovering the shoreline are things to be done in complete safety by limiting as much as possible the risk of a breakdown. Undertaking periodic engine maintenance means your outboard will be reliable and operational in the long term.
Just when you don’t need it, outboard motors can make a nuisance of themselves...
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Oliver Barret
Publié le 25/05/2023
Par Oliver Barret
Numéro : 190
Parution : Jul. / Aug. 2023
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Multihulls World #190
Even though most manufacturers are getting ready for a transition to electric, most of our tenders are still equipped with four-stroke internal combustion engines. When compared to the 2-strokes of times past, these motors are almost marvels of technology. Quieter and more sober, 4-stroke engines do however require some care and precautions to keep them working properly. What’s more, increasing prices mean you’ll want to keep them in good shape for longer. There’s nothing worse than having to paddle because the engine has stalled and won’t restart, or to hear the dealer suggest you sell your engine for parts when you were still hoping for a miracle. Careful operation and meticulous maintenance are obviously the key to the reliability and longevity of an outboard motor, that’s likely exposed to spray either on a bracket on deck or on the dinghy when it’s on the davits at the stern of your multihull. Like an inboard engine, the moving parts need both cooling and lubricating. These two points are essential to the life of your engine, but it isn’t that complicated to deal with either of these, even in the most remote anchorage, provided you have the necessary equipment of course - but that should be part of your on-board equipment anyway. On the other hand, the fuel system and electrics must also be the subject of attention. When in constant use on the transom of our dinghies, outboards are subject to large variations in temperature and humidity, which can cause damage to fuel connections and impact fuel quality. We discuss flushing, draining and electrics parts in detail. In a future issue, we’ll take a closer look at how to fix fuel feed problems and carburetor maintenance.
Philippe Bauer from Tendance Voile agreed to let us follow a full service and winterization of an 8 HP Yamaha 4-stroke outboard engine and a 5 HP Mercury with an integrated tank. Philippe tells us from the outset that engines of 10 to 15 HP and more have become so complex in terms of electronics that there is really no other alternative than to take them to a professional - and that’s better for the warranty too.
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If you’re laying up for the winter - or making a long stopover in port - this is the time to deal with engine maintenance. Beware, an 8 HP 4-stroke outboard (or this rustic 18 HP 2-stroke) can already weigh getting on for 90 lbs (40 kg), so it might be useful to have an extra pair of hands. Basic maintenance should take between one and two hours... And with a little courage, let’s get on with it!
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Downloading the genuine user manual is a good idea. Most maintenance guides can be easily found on the internet.
A large container or drum can be used to flush the cooling system with fresh water. Leave the engine running for 5 to 10 minutes, checking that water is discharging from the outlet. Then disconnect the fuel supply hose (located inside the cowling on a motor with an integrated tank) and wait for the engine to run out of fuel. Finally, completely empty the carburetor float chamber by pulling on the starter cord several times.
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Flushing

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Flushing is an essential part of the operation. It should be done at least once a year, but better to do it as often as possible and especially if the outboard is going to be left unused for a couple of weeks or more. Some motors are equipped with a connection for attaching a hose to the intake. This operation can then be done on the davits if the outboard is accessible.
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When recommissioning after winterization, do not reuse “old” gasoline that is likely full of bacteria. Drain the fuel tank, clean it, and start over with new gasoline. An integral tank can be easily removed for this purpose.

Engine maintenance

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For this operation, we recommend installing it in a comfortable position to work on - ideally, the motor will be well secured on a proper stand. Prepare all your kit beforehand so that you don’t forget any steps.

Ignition

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Remove the spark plug and check its condition. If you hold against the block and pull the starter cord, it should spark. Descale it or change it if it looks worn or blackened.

Changing the oil

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Depending on the model, the drain plug is located on the leg or beneath the engine block.
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Undo the bung using the appropriate tool and collect the oil in an old can.
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The oil capacity and type (viscosity) are often shown on the cowling or on the integrated tank for smaller engines. But if not, the user manual will provide this information.
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Refilling can be done with a large syringe that you fill from a jam jar (proper boaters know how to improvise!). You’ll have to repeat the operation seven or eight times to fill the 0.8-liter (almost a quart) capacity.
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Check the level periodically while continuing to fill up to 90% of the capacity. Topping-up is carried out after an initial restart, after allowing the oil to circulate.

Changing the gearbox oil

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Slacken off and undo the bung in the gearbox casing and recover the used oil in an old can, to be disposed of properly at the waste oil point at the next port of call.
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The oil must be filled until it just starts to overflow from the upper hole, then the bungs are replaced, starting with the lower one.
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The special gear oil is filled in via the lower hole by simply squeezing the tube. If there’s not enough pressure, you can jury-rig a pump system.

Greasing the shafts

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Clean and grease the motor tilt shaft. The vertical rotation shaft bearing should be carefully greased using a proper grease gun - this a moving part, immersed in water, that can be susceptible to rust.
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A good clean with WD40 is required to get rid of any salt build-up on the engine block itself, and to protect the electrical connections. Take the opportunity to give a little squirt on the starter system and pull it two or three times. If it’s too hard, remove the cowling and undertake a thorough clean.
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If the anode is too corroded, it must be replaced. If the motor is being winterized, adding a small label will help you remember what was done or not done before recommissioning it.
Tags : maintenance , outboard motors

Numéro en cours

MM233 - octobre-novembre 2025

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