How should I winterise the engine on a Beneteau Oceanis 38?

Winterise your Oceanis 38 by changing the engine oil and filters, protecting the seawater circuit with suitable antifreeze and checking frost protection in the separate freshwater coolant circuit. Service the fuel system and fully charge the batteries too; antifreeze at the exhaust confirms only that fluid has passed through the seawater side.

Identify engine and cooling circuits

Read the engine identification plate and find its handbook. Oceanis 38 installations commonly have a Yanmar diesel, but the engine model, service quantities and saildrive equipment vary with build year and specification. Order parts against the engine number.

The engine normally has two cooling circuits:

• Freshwater circuit: coolant circulates through the engine and heat exchanger, usually also serving the calorifier. It stays filled during winter.
• Seawater circuit: water passes through the intake, strainer, raw-water pump and heat exchanger before entering the exhaust mixing elbow and waterlock.

With the engine cold, check the coolant level, look for leaks and measure antifreeze strength with a tester suitable for that coolant. Protection must cover the lowest likely storage temperature. Replace overdue or unidentified coolant with the engine manufacturer's specified product; colour alone does not identify compatibility.

Change oil and filters

Service the engine before storage so it spends winter with clean oil. Run it to normal operating temperature with its cooling supply intact. Stop it, then extract the warm oil through the approved extraction point.

1. Replace the engine oil filter, making sure the old rubber sealing ring comes away.
2. Refill with the handbook's specified oil grade and quantity, then set the final level using the dipstick rather than relying solely on the quoted capacity.
3. Run briefly and check for leaks. Stop, allow the oil to settle and recheck the level.
4. Inspect belts, hoses, hose clips, engine mounts and the exhaust mixing elbow for wear, leakage or corrosion.

Check saildrive oil separately, following its manual. Milky oil suggests water ingress and needs investigation before storage. Inspect the raw-water impeller and account for any missing blades; fragments can lodge at the heat exchanger inlet.

Protect seawater circuit and exhaust

Use a marine winterising antifreeze suitable for engines and wet exhausts, mixed for your expected minimum temperature. Check whether the stated protection refers to freezing or bursting. These are different ratings.

Keep clear of belts and pulleys, ventilate against exhaust fumes and never run the engine without a cooling-water supply.

1. Close the seawater intake seacock before disconnecting the intake hose or opening the strainer.
2. Arrange a secure supply from a container through the engine's approved winterising connection or disconnected intake hose. Keep the container replenished so the pump cannot suck air.
3. If flushing with fresh water first, let the engine pump draw it from the container. Do not connect pressurised mains water directly to the engine.
4. Draw through enough antifreeze to displace the remaining water and protect the circuit. Exhaust colour alone is unreliable because residual water dilutes the mixture. Check the discharged mixture with a suitable tester.
5. Stop before the container empties, reconnect hoses securely and label the controls to prevent an unprepared start.