How should I winterize the engine on a Najad 361?

Winterise your Najad 361 by changing the engine oil and filter, checking the closed-circuit coolant's frost protection and flushing and frost-proofing the seawater circuit. Check the engine identification plate and manual first: many 361s have a Volvo Penta MD22-series diesel, but replacement engines and different installations mean quantities and drain points vary.

Check your engine installation

Find the engine model and serial number, then locate the seawater inlet seacock, strainer, raw-water pump, heat exchanger and exhaust waterlock. Trace the connections between these parts; antifreeze poured into the engine's coolant header tank does not protect the separate seawater circuit.

Check the manual for oil specification, sump capacity, coolant type and any specified seawater drain points. Buy the correct oil filter, replacement sealing washers, suitable oil, coolant-compatible antifreeze and a marine winterising fluid approved for the engine's raw-water components.

Budget roughly £80 to £150 for a basic DIY oil, filter and winterising-fluid service, depending on the engine and products. Fuel filters and an impeller cost extra. Do not take capacities from another Najad's engine.

Change the oil while warm

Change the oil before frost-proofing the seawater circuit: warming the engine afterwards would wash out the winterising mixture. Old oil carries soot and combustion contaminants. Leave clean oil in the engine over winter rather than postponing the change until spring.

1. Run the engine with its normal cooling-water supply until warm, checking that water leaves the exhaust.
2. Stop it, extract the oil through the designated extraction pipe or dipstick tube, and remove the filter.
3. Check that the old filter seal has come away, lightly oil the new seal and tighten the replacement as its instructions specify.
4. Add the specified oil progressively, checking the dipstick rather than pouring in the full nominal capacity.
5. Run briefly and inspect for leaks. Stop, let the oil settle and recheck the level.

If you remove a drain plug, tighten it to the torque specified in the engine manual; there is no universal MD22 or Najad drain-plug setting. Inspect belts, hoses, clips and engine mounts while access is open.

Protect both cooling circuits

Test the closed-circuit coolant with a tester suitable for its glycol type. Protection to around minus 25°C is a sensible target for many northern European lay-ups, but follow the engine manual and expected local minimum temperature. If the coolant's age or chemistry is unknown, replace it with the specified type. Colour alone does not establish compatibility.