Engines

Top tips for repairing them yourself
Aboard a sailing multihull, mechanical propulsion is, in theory, auxiliary. But if you’ve got to get out of a heavy weather situation, or simply maneuvering in port serenely and efficiently recharging your batteries, having engines is obviously preferable. In the case of a power-driven multihull, obviously things are different: you expect to hear the engines fire up when you press the ignition switch... 
It doesn’t run? It doesn’t run well? It’s overheating? Let’s take a look under the hood!
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Olivier Barret
Publié le 01/02/2023
Par Olivier Barret
Numéro : 188
Parution : Mar. / Apr. 2023
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Multihulls World #188
Remember that on board a catamaran, you have two engines. And that’s obviously reassuring, as total engine failure is extremely rare. Experience shows that on modern multihulls, most breakdowns are electronic in origin and most often occur for want of maintenance. Various messages come up on the display screens. If these aren’t critical, they can be deleted provided their content has been taken into account and can be recalled the next time routine maintenance is undertaken. In the event of a more serious problem, the engine management system will prevent you exceeding 1,800 rpm, but thereby still enabling you to return to the nearest port. Afterwards, you will have to call the brand’s dealer because they will be the only ones who can intervene. The life of a well-maintained diesel engine is estimated at 7,000 to 10,000 hours. Our report was done on board three Fountaine Pajot catamarans – an MY 37, an Astrea 42 and an Elba 45. Some photos, taken before the maintenance, show traces of oxidation on components that could have led to a breakdown. Scheduled inspections and maintenance, correctly carried out, will obviously be the best guarantee of optimal reliability.
In this article, we’ll focus on units under 60 feet, and begin by making the assumption that the engines have been correctly maintained to date. For now, we’ll ignore what you might call “external” problems such as a line round the propeller (a classic subject that deserves its own article!), to focus on the most common failures under way. These can be summarized as three phenomena, namely, electrical problems, fuel supply, and overheating. The breakdowns described below should be solvable without assistance, and using the tools and spare parts that should be in the inventory of any cruising multihull. If after all these checks the engine still won’t start, the help of a professional will become unavoidable. We would like to thank Tendance Voile for their friendly and instructive assistance in writing this article.
The drivetrains on recent, powerful models over 60 feet in length can be very complex. If you’re looking at a significant engine failure, only a main dealer can intervene, by plugging it into their computer. But don’t worry, in many cases, this can be done remotely!
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1 - Starting

If the starter motor doesn’t work, check that the engine starter battery terminals are securely connected. The terminals may also be corroded.
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Check the position of the emergency stop on the top of the engine – here, on a Yanmar, the red button. If it’s on stop, the engine isn’t going to start.
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If both motors are connected to the same battery bank, start the one that is powered first - meaning the one that is closest to the batteries. Doing the opposite may cause a system error to appear on the control screens.
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2 - Fuel circuit

First, check for water or dirt in the separator bowl under the diesel prefilter and drain/bleed if necessary. There is a water sensor beneath the filter: if there’s water present, you should get an alarm on the display.
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Check that diesel is getting through by pushing the priming button. If fuel is not flowing, check the pickup pipe - it may be clogged with dirt in the tank.
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If the fuel has been in the tank for a long time, deposits can form, and the filter can become so dirty that the fuel no longer passes through. If this is the case, you’ll need to change the filter and prefilter.
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At sea, it’s easy to deal with - provided you have one or more jerry cans of clean diesel. The hose coming from the tank is disconnected at the lift pump. In its place, you connect a hose from the can and re-prime the circuit, then restart the motor.
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3 - Overheating

First, make sure the raw-water cooling system is working. Outside if the exhaust is above the surface. If the exhaust is below the waterline, check to see that water is bubbling through the strainer.
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Having first ensured that there’s no blockage in the raw water intake, check the coolant level.
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Also check the drive belt that turns the raw water pump. It’s important to inspect for wear or whether it grooved and, above all, correctly tensioned. You should be able to twist it, and also depress it by about a finger’s width.
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To re-tension the belt (or change it) the adjustment is most often found at the alternator.
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The impeller may be defective. If so, it should be replaced with a new one. Lubrication is essential when refitting - as is a new coverplate seal.
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Becalmed with exhaust elbow trouble – it can happen! You’re recommended, once the engines are warmed up, to give it a bit of maximum revs every trip, to keep the exhausts clean.
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Multihulls World top tips

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Make sure you’ve got all the essential spare parts on board (belts, impellers, filters, hoses, pipes, etc.) and a full set of tools!
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MM233 - octobre-novembre 2025

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