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Engine cooling systems.

Am I right in thinking that you can't use a raw water cooled engine in freezing weather because you have to drain it? Not for a continuous cruiser then?

Asked by: Carl Young  | 8.10pm, Tuesday 1 May


WW says:

It is certainly possible to use a raw water cooled engine in freezing weather. All the motor driven carrying boats up to the 50's had raw water cooled engines.
The real problem comes when you stop, and that depends on where the engine is within the boat, and how long it will be stopped. If it is a cruiser style narrowboat, the engine will get colder than one in a traditional engine room, which will be warmed from the cabin. Modern engines are lighter and have less thermal mass than the older heavier lumps. Unless the canal is frozen solid, the liquid water outside the boat will keep everything below the water line from freezing for short periods.
If you are running the engine everyday you will not have to drain a raw water cooled engine. If however the engine is to be left at the mercy of the elements, it and the pump will need to be drained.

Rupert Smedley  | 11.10PM, Tuesday 1 May

It is certainly possible to use a raw water cooled engine in freezing weather. All the motor driven carrying boats up to the 50's had raw water cooled engines.
The real problem comes when you stop, and that depends on where the engine is within the boat, and how long it will be stopped. If it is a cruiser style narrowboat, the engine will get colder than one in a traditional engine room, which will be warmed from the cabin. Modern engines are lighter and have less thermal mass than the older heavier lumps. Unless the canal is frozen solid, the liquid water outside the boat will keep everything below the water line from freezing for short periods.
If you are running the engine everyday you will not have to drain a raw water cooled engine. If however the engine is to be left at the mercy of the elements, it and the pump will need to be drained.

Rupert Smedley  | 11.12PM, Tuesday 1 May

Just to note there is a difference between raw water cooled engines (where the canl water circulates around the engine, as in traditional narrowboat engines) and fresh water cooled engines.
With these, antifreeze solutions (the freshwater part) circulates around the engine, and then passes through a heat exchanger, where the canal (raw) water passes through to cool it, before being dumped into the exhaust to cool it.
Freshwater cooling is more complicated, but this is how most modern engines (apart from keel cooled narrowboat engines!. It means that the engine can work at an effective (70 to 90 deg C) temperature, rather than the 40 to 60 deg C that raw water cooled engines run at (which is more inefficient- but higher temperatures can lead to sludging).
With freshwater engines, if you are not cruising, and going to leave the boat, you also need to drain the heat exchanger (the most expensive bit) via the drain plug. you should also drain the exhaust sump (waterlock) if fitted, though this isn't critical.
Many river cruisers and seagoing boats work all year round very well in freezing conditions with fresh (and raw) water cooling : the advantage is that they are more thermally stable and the exhaust can be silenced more- and the engine room can run cooler.

Mark Langley  | 10.01AM, Wednesday 2 May

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