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How to winterise your boat

Follow our top tips to successfully winterise your engine and your boat will thank you for it at the start of next season!

Winterise your engine with an inspection:

To winterise your engine effectively, begin with a thorough engine inspection. Use ample lighting, mirrors on sticks, or digital cameras to inspect all engine components, including the exhaust. After changing oil, filters and coolant, ensure that the bilges under the engine are completely dry to prevent corrosion. For vessels with inboards, consider painting them white to easily detect and future leaks 

Highfield Sport

Fuel Tank Maintenance:

If your boat is being stored for the winter, fill the fuel tank to the brim to prevent condensation increasing the water content of the fuel and the growth of ‘diesel bug’ on inboard diesel vessels which can be prevented by using a fuel treatment.

Oil Change:

Change the engine oil and replace the oil filter before winter. Leaving old, contaminated oil inside the engine can shorten its lifespan and cause expensive damage.

Gearbox Inspection:

Check the gearbox or outdrive oil before leaving the boat ashore for winter. Replace if it appears cloudy or milky.


Ensure you run the engine with fresh water and an antifreeze agent to protect from freezing over the winter. Water usually drains out from the self-draining water passages, but this is a full-proof plan.


Most diesel engines use a combination of raw water and freshwater cooling, both of which require attention during winterisation. Drain the cooling system before hauling out, then refill it with a strong antifreeze solution. Running the engine will help circulate the new solution and prevent damage from freezing water.

Honda outboard

Air Intake Protection:

Remove the air intake filter in the autumn and stuff the intake with an oily rag to prevent rusting. You can also add a bit of oil and turn over the engine (without starting) to distribute it over the cylinder walls.

Battery Care:

Keep batteries warm and dry over the winter, ensuring they are fully charged or topped up every four to six weeks. Disconnect batteries from the electrical system, clean and grease the terminals to prevent freezing in sub-zero temperatures.

Belt Maintenance:

On belt-driven diesel and petrol inboards, relax or remove all belts and protect the drive wheels to prevent rust, which can damage belts in the new season.

Highfield and a Honda Outboard

Proper Angle:

Ensure the boat is slightly angled bow upwards to facilitate immediate run-off of rainwater from covers, decks, and the cockpit. Use covers that keep water out while allowing air circulation to prevent condensation, dry rot, mould and corrosion.

Interior Care:

Store all linen, clothing, blankets, curtains, etc, ashore after washing and drying. Keep the fridge door open to prevent mould growth. Promote ventilation by leaving cupboards, drawers, and under-berth locker lids open.

Electronics Protection:

Use tight-fitting covers for deck-installed electronics and consider applying water-repellent silicone behind them. Inspect navigation lights for range, bearing, wiring and any damage to their covering. Please remember, Sail Shape Marine’s sister company Sail Shape Ltd manufactures bespoke covers on site.

If you are feeling confident and are mechanically minded, you can winterise an engine yourself. However, if you’re in any doubt, please contact the team at Sail Shape Marine to book in your winterisation.

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