How should I winterize the engine on a Bavaria 37 Cruiser?
I'm laying up my Bavaria 37 Cruiser ashore for the winter and want to service and frost-proof the diesel myself. What should I do about the cooling water, oil, fuel and saildrive before leaving her until spring?
Answer
Winterise your Bavaria 37 Cruiser by changing the engine oil and filters, protecting the seawater cooling circuit with suitable antifreeze, and checking frost protection in the separate engine coolant circuit. Check the fuel system and saildrive, fully charge the batteries, and record anything disconnected or closed.
Identify the engine and cooling circuits
Read the engine identification plate and its operator's manual first. Bavaria fitted different engines during the 37 Cruiser's production, and replacements are common. Older boats may have a Volvo Penta MD2030, while later examples commonly have a D1-30. The boat's name alone cannot tell you the oil capacity, filter numbers or drain locations.
These engines normally have two cooling circuits. Freshwater coolant circulates inside the engine through a heat exchanger. Seawater passes through the other side, then enters the exhaust. Protecting one circuit does not protect the other.
- With the engine cold, check the coolant level and inspect hoses, clips, the seawater strainer and pump cover for leaks.
- Test the engine coolant with a tester suitable for its glycol type. Choose protection below the lowest expected local temperature.
- Identify the existing coolant specification before topping up. Similar colours do not mean coolant types can be mixed.
Never remove the coolant pressure cap while the engine is hot.
Change oil and filters
With the cooling-water supply established, run the engine to normal operating temperature. Stop it and extract the warm oil through the designated extraction point or dipstick tube. An oil change removes soot and contaminants that would otherwise sit inside the engine all winter.
- Replace the oil filter, making sure the old sealing ring comes away with it.
- Refill with the oil grade and quantity specified for the fitted engine. Check the dipstick rather than pouring in an assumed capacity.
- Replace the engine fuel filter and primary filter element as required, drain water from the separator, and bleed according to the manual.
- Run briefly and inspect for oil and diesel leaks. Stop, let the oil settle and recheck its level.
Complete these running checks before the final antifreeze treatment. Inspect the alternator belt and seawater impeller. Replace the impeller if its blades are cracked or hardened, or if any are missing. Recover missing pieces from downstream passages.
Protect the seawater circuit
Use antifreeze intended for marine engine winterisation and compatible with the cooling-system materials. Mix it to the manufacturer's instructions. The container's burst-protection rating is not necessarily its freezing point, and residual flushing water weakens the mixture.
Keep clear of belts and pulleys while the engine is running. Never run it without an uninterrupted cooling-water supply.