Diesel motor care and maintenance

Table of Contents


  1. Winter protection during the warranty period

Oil & filter change

  1. Engine & transmission oil change
  2. Oil filter change


  1. Tighten or replace V-belts

Winterising boat engine fuel & cooling systems

  1. Fuel system
  2. Cooling system

Lubricating engines & inspecting engine bellows

  1. Lubricating diesel engines
  2. Inspecting engine bellows

Diesel motor care and maintenance

Engine malfunctions often occur during the winter break due to rust and frost. So, it's important to prepare boat engines well for the cold season. Our SVB engine experts explain the most important wintering tasks in a clear and concise way.

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Can I winterise my engine myself?

During the engine’s warranty period it is recommended to have the engine prepared for the winter by an authorised service centre. Once the warranty has expired, with a little skill you can winterise the engine yourself. Start to winterise your engine with your boat still in the water. Use a sponge and detergent to remove dirt from the engine and examine it for scratches and rust.


Why change the oil of diesel boat engines and what to watch out for.

It is important to change the engine and transmission oil before storing the boat for winter, as used oil contains acids that can damage the metal of the engine. Other pollutants and possible water residue can also damage the engine over the winter. If your compressor and injection pump have separate oil systems, an oil change is also necessary.

First, let the engine warm up to make the oil thinner. It can then easily be pumped into a jerry can or oil canister using a suction pump. Top up with new oil according to the instructions in your engine manual.

If you want to preserve the engine for longer than just the winter break, we recommend special preservation oil. In this case, the oil must be changed again at the start of the season.
Changing the oil before winterising your engine

How do you change the oil filter on boats?

How do you change the oil filter on boats?

All filters can easily be changed using a filter key or filter belt. When loosening and unscrewing the oil filter, it is recommended placing a bowl under the filter and keeping a cloth ready, as dripping into the bilge can occur.

How do you change the oil filter on boats?

Check that the rubber seal is in the correct position and lightly coat the contact surface with oil to prevent the rubber seal from slipping. Tighten the new oil filter by hand. Allow the engine to run for a few minutes to distribute the oil and then check the filter for leaks.

When should I replace or retighten my boat engine V-belt?

Storing your engine for winter provides a good opportunity to check your V-belt for possible damage and sufficient tension. Frayed or damaged belts must be replaced. V-belts that yield more than 10mm when the thumb is pressed against the middle of the belt must be retightened. A description of how to do this is given in your engine manual.

Checking v-belts before winterising
Servicing boat engine fuel systems

How do I protect and care for the engine fuel system?

First empty the water separator. To do this, open the drain screw and let the water flow into a bowl until only diesel comes out. Then replace the filter cartridges and filter inserts and bleed the engine according to the instructions in your engine manual. Finally, add a fuel additive to the tank that removes deposits, absorbs moisture and protects the engine against corrosion, preferably when the boat is still in the water. It is necessary to allow the engine to run for more than a few minutes to allow the agents to work.

Winterising boat engine cooling systems Winterising boat engine cooling systems

What should I keep in mind when wintering the cooling system of boat engines?

Start wintering the cooling system only when on land. First check the internal circulation system for sufficient antifreeze and top up with antifreeze if necessary. In this case, allow the engine to run for a few more minutes so that the coolant and antifreeze mix and are well distributed. Then check the antifreeze again.

Next, thoroughly flush the seawater circulation system (seawater filter, pump, gearbox and exhaust system) with fresh water as described in your engine manual. This can be done by running the engine with a rinse connection, or alternatively by disconnecting the cooling water intake hose from the seawater filter or bottom valve and connecting it to a water tap with a garden hose. There must always be enough water to ensure that the engine does not run dry.

As soon as possible after draining, with the thermostat still open, the cooling system should be preserved with antifreeze. For optimal frost protection, we recommend a mixture that can protect from -25° celsius. Close the seawater valve for cooling water intake and, at idle speed, simply let the pump suck the antifreeze fluid in via a hose, e.g. the disconnected cooling water suction hose, and run through the cooling system. Alternatively, pour the antifreeze directly into the seawater filter when it is screwed in. In both cases, allow the engine to run until coloured water comes out of the exhaust.

Wintering the cooling system also includes checking the seawater pump. To do this, pull the impeller out of the pump and check for damage after rinsing. During the winter, the impeller should be kept in a dry place and fitted with a new seal in the spring. It is recommended to always have a spare impeller on board. If the impeller pump is installed in the z-drive, always have the inspection carried out by a specialist.

The strainer should also be removed and cleaned. Check the hoses and hose clamps and replace if necessary.

Which parts of my diesel boat engine require lubricating before wintering?

Lubricate the grease nipples & moving steering components. The location of the grease nipples and which grease to use can be found in the engine manufacturer's operating instructions.

Lubricating diesel engines

Why should I inspect my engine bellows before wintering?

Check the bellows/collar for damage and porosity. A leaky bellow can allow water to enter the drive shaft, which can lead to extensive damage. For this reason, it is always recommended to use a new bellow, if in doubt.

The exact steps for wintering your engine type can also be found in the operating instructions for your diesel engine.

Inspecting engine bellows
Written by our SVB (technical) experts

Written by our SVB (technical) experts

Our team of SVB technical experts is there to give our customers professional advice on all matters relating to technology on board. Their expertise is the result of regular training and many years of experience.