How to Protect your Sailboat Engine in Winter

Winterising your sailboat engine is crucial for protecting one of the most expensive and essential components of your boat. If left unprepared for the cold months, your engine could suffer from corrosion, rust, and even freezing damage, leading to costly repairs come spring. By following a few key steps, you can ensure that your sailboat engine remains in top condition, ready for action when the sailing season starts again.

Flush the Engine

The first step to preparing your engine for winter is to flush it with fresh water. This is particularly important for saltwater sailors, as salt can corrode engine parts if left sitting over the winter months.
• Why it’s important: Salt and debris can cause significant corrosion if not flushed out, and fresh water removes these harmful elements.
• How to do it: Run fresh water through the cooling system to eliminate any salt or sediment buildup. For outboard engines, use a flushing attachment; for inboards, you may need to use the water intake system.

Drain the Cooling System

If water remains in the cooling system, it can freeze and cause the engine block or other components to crack. Draining or replacing this water with marine antifreeze is essential to avoid these potentially expensive damages.
• For inboard engines: Drain the water or use marine-grade antifreeze to ensure that the cooling system is safe from freezing. Circulate the antifreeze through the system until it comes out of the exhaust to know it’s fully protected.
• For outboard engines: Tilt the engine to its lowest position and allow the water to drain completely from the system.

Change the Oil and Filter

Old oil left in the engine over winter can cause corrosion due to the moisture it collects. Changing the oil and filter before winter ensures that fresh, clean oil coats the internal parts, preventing rust and other damage.
• Warm the engine first: Run the engine for a few minutes to thin the oil, making it easier to drain. This also helps to remove any contaminants.
• Change the oil and filter: Refill with fresh marine engine oil and replace the filter to ensure the engine is protected over the winter months.

Fuel Stabilisation

Fuel can degrade over time, especially during periods of inactivity. This can lead to clogged fuel lines or injectors, making it harder to start the engine in the spring. Adding a fuel stabiliser helps keep your fuel fresh and prevents gum and varnish from forming in the fuel system.
• How to apply it: Add the stabiliser to the fuel tank and run the engine for a few minutes. This will circulate the treated fuel throughout the system, protecting it during storage.

Apply Fogging Oil

Fogging oil is a protective lubricant that coats internal engine components, preventing rust and corrosion during long periods of storage. It’s essential for both inboard and outboard engines.
• For outboards: Spray the fogging oil into the intake while the engine is running at idle.
• For inboards: Spray it into the spark plug holes or carburettor. This provides a protective layer on pistons and cylinders, guarding against moisture-related damage.

Taking the time to winterise your sailboat engine can save you from costly repairs and extend the life of your engine. From flushing and draining the cooling system to adding fuel stabilizer and applying fogging oil, each step plays a vital role in protecting your engine during the off-season. With a little effort, you’ll ensure that your sailboat is ready to hit the water again as soon as the warm weather returns.
Make sure to also check out our guide on preparing your boat for winter, covering all the steps from protecting the plumbing system to keeping your boat’s interior free from moisture.
You’ll also find all boat winterising products you’ll need at the best prices on our site, from boat dehumidifiers and boat heaters to marine engine oils.