Poor maintenance can often do more damage to an outboard motor than high usage can. So during the winter and off-season, it is important that the maintenance of your outboard isn’t neglected. As well as ensuring that your outboard is kept up to date with servicing, it is vital to ensure that it is also properly winterised. Failure to properly winterise an outboard motor can result in serious and possibly even terminal damage to it.

Whilst some people may try and undertake the winterising process themselves, unless you are highly skilled and knowledgeable in the area, we would always recommend that you use an approved outboard service centre, such as MB Marine, to carry out the work for you. This is especially important if your outboard motor is still under warranty, as failure to properly maintain and service your outboard as per the manufacturer’s guidelines, can invalidate your warranty.


Winterising is the process of getting an outboard motor ready to be put away in storage for the winter. The winterising process covers a number of key procedures, that if not carried out before being put into storage, can cause the motor to corrode, seize and ultimately land you with a large repair bill.

For more information about our Winterising service, call us on 02380 388 608 or email sales@mbmarine.co.uk.



Flushing the Engine - Saltwater can be highly corrosive to metal, so to avoid internal corrosion of the engine’s aluminium waterways, it is vital that outboards are properly flushed with clean water before they are put into storage.

Treating the Fuel - Fuel does not store well in engines and can lead to corrosion, so it shouldn’t be left untreated in the tank over winter. Part of the winterising process is to add a stabilizer to the fuel.

Inhibiting the Engine - In order to protect the inside of the engine whilst it is in storage, it is important to add a coating of fogging oil to bores. This will coat the inside of the engine in a protective film, protecting parts such as the big ends, cylinders and valves.

Applying Corrosion Guard to Engine - Corrosion Guard spray is applied to the engine’s metal and painted surfaces, to help prevent rust and corrosion from forming. It will also be applied to any existing patches of rust or corrosion to prevent them from worsening.


Draining the Engine Cooling System - To avoid the risk of damage being caused by water freezing and expanding in the motor whilst it is in storage during cold weather, it is thoroughly drained of water.

Checking and Replacing the Spark Plugs - Spark plugs are checked both for their condition and the electrode gap and are replaced if necessary.

Checking and Replacing the Engine Oil - Engine oil deteriorates over time as it absorbs moisture and gets contaminated, so checking the oil is part of the winterising process.

Checking and Replacing the Gear Oil - As with engine oil, gear oil can also deteriorate in quality, so this will also be checked and replaced at the same time. We always use proprietary outboard oils to ensure they contain the correct additives for use in water.

Greasing Moving Parts - It is vital to apply water-resistant grease to all moving parts of the outboard before placing it in storage. This includes the propeller shaft, joints, cable ends, nuts and bolts and other grease points prone to seizing.

FAQs Frequently asked questions relating to outboard motor winterising

What will happen if I leave water in my outboard motor?

If you leave water in your outboard motor for any length of time when it is not being used, you run the risk of severe and very costly damage. As temperatures plummet during the winter, any water that has been left inside the motor will freeze and expand, causing cracks and other damage to occur internally. Additionally, salt water is corrosive and can cause corrosion within the engine.

Do both 2 stroke and 4 stroke outboard motors need to be winterised?

Yes. While the exact process varies slightly, all outboard motors, both 2 stroke and 4 stroke, should be winterised to prevent damage.

Do I need to winterise my outboard motor, even if it is going to be stored indoors over the winter?

Yes. Whilst some of the winterisation process is to prevent damage caused by freezing temperatures, other aspects of the process, such as replacing oils, treating fuel and greasing moving parts should be carried out if an outboard motor isn’t going to be used for a long period of time, regardless of the temperature.

When should I winterise my outboard motor?

You should winterise your outboard motor as soon as the temperature drops sufficiently that there is a risk of frost and you have finished using your boat for the season. In the UK, this is usually around the end of September.

When should I de-winterise my outboard motor?

It is safe to de-winterise your outboard motor as soon as the last of the spring frost has passed. In the UK, this is usually around April.