diesel inboard boat engine

Properly maintain the boat engine


This is how you get your yacht ready for a successful season on board!

The requirements for boat engines are high and very different. The maritime environment brings with it special challenges and the reliability of the drive is an important safety aspect for the skipper and crew.

Almost more important than the spring overhaul, which we are about to come to here, is the wintering work for boat engines. The main aim here is to protect the common built-in diesels from frost and rust.

There is a lot of truth in it, because if a diesel engine is serviced even halfway regularly and treated sensibly during operation – let it warm up to operating temperature before it is stressed, do not switch it off again after a few minutes and, in the case of sailing yachts, not “motor sailing.” “, Because if the yacht is heeled under sail, the lubricating film in the motor can tear off, with often fatal consequences – it can run for many thousands of hours. It is bad for the engine if it stands too long and then, above all, has not been properly preserved.

Fresh oil is a must

But let’s get to the happy spring. The antifreeze from the cooling circuit should be collected and disposed of if possible. After the long winter you should definitely change the oil and treat yourself to the good piece of fresh oil, because this vital lubricant can sometimes decompose or otherwise degenerate over the winter and regular oil changes are simply part of the standard for maintaining the engine.

Oil change, filter change & Co

A proper oil change always includes changing the filters, especially the oil and diesel filters, as well as a new impeller. You should also renew it once at the beginning of the season, which is always better than having to do it sometime during the summer.

There is not much to say about the oil change: suction with a hand pump (at operating temperature) from the oil test port or, if it is a newer engine, suction from the specially provided port, usually somewhere on the side of the engine block. If the oil filter is changed regularly, it shouldn’t be too difficult to remove. Before you put on the new filter and screw it on (“warm to the touch”), you should thinly smear the rubber seal with grease or diesel – then it can be easily removed a year later. If the oil filter has not been changed for a long time and is stuck, unfortunately only the brute method sometimes helps: Push a large, sturdy screwdriver through it and then use this lever to unscrew the filter. There is also a special tool with a tightening metal loop to remove stubborn filters, but this is usually only available to the engine professionals themselves.

Diesel filter & impeller

When changing the diesel filter, check the lines for any leaks. Because in the worst case, air can enter here and stop the engine. Depending on the make and model of the motor, changing the impeller can be very easy or a horrific fiddling around. Usually the impeller housing is easily accessible at the bottom and front of the engine, but on some models (from Yanmar, for example) the water pump is still in front of it. In such a case it is usually easier and quicker to unscrew the pump to get to the impeller housing, instead of fumbling around blindly and with bent fingers behind the pump.

V-belts & spark plugs

Finally, check the V-belt tension and, if necessary, retighten it. Incidentally, impellers and V-belts are wearing parts that always belong on board as a replacement. In the case of gasoline or outboard engines, check and clean the spark plugs or replace them if necessary and the good piece is ready for the season.

Propeller & shaft

But the drive system goes even further outside, outside the fuselage. Is the propeller firmly seated on the shaft? Has the wave no game? If the zinc anode on the shaft is still in good condition – as stated elsewhere in this series, it should be replaced when only 50 percent or less of the original is left. And of course it shouldn’t be painted over either. Folding propellers should be made operational and re-greased. With a saildrive, the rubber sleeve on the hull has to be replaced every few years.

With these simple measures you should get your engine through the season well. If, on the other hand, the engine does not run smoothly, suffers from starting problems, or if it smokes a lot after starting (whitish or dark), then it is unfortunately more time to decide on a professional engine overhaul, which is a case for a specialist is.

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