Engine Water Cooling

[jamie]

I have a 30 ft Steel motorsailer and i am having a recon engine fitted(BMC1800)
i have been told by the person fitting it that i would be better having it bilged cooled and not raw water cooled.I am concerned about it over heating and any affects at high angles of heel.

 

[dickh]

Not sure what you mean by "bilge cooled", I am assuming you mean Fresh Water Cooled with a Heat Exchanger. With this the cooling water for the engine is a closed system(like a car & radiator), the system has a thermostat like a car, and instead of a radiator you have a heat exchanger which is cooled by sea water which is then injected into the exhaust to cool it and then shot out with the exhaust gases. This is a very common and well proven system and has the advantage that there is no internal engine corrosion from sea water and the engine runs at the correct temperature. You should have no problem with overheating as the inlet pipe to the sea water should be close to the keel.
OR do you mean "Keel Cooling" - this is where in place of the heat exchanger there are pipes parallel to the hull on the outside, the hot engine water is pumped through these and then cooled by the sea water.
DON't go for Raw water cooled, the engine won't last five minutes, you will only be able to run the engine at 60ºC max and you will get serious internal corrosion.

dickh
I'd rather be sailing...

 

[bryantee]

Fitting keel cooling on a steel hull is reasonably easy.use channel section ,not pipe and have a tee section at the bottom end of the U ,to fit a drain/flushing cock.
good luck

 

[oldharry]

Many of the old BMCs were raw water cooled and survived it for a very long time. The only problem was that the core plugs used to rust out and fail with - er - interesting consequences! carrying some spares was mandatory with raw water cooled BMCs.

Otherwise, internal corrosion tended not to be much of a problem with BMCs. What DID tend to happen was that the engine waterways got clogged up with sand and silt resulting in increasingly poor circulation, leading to localised 'hot spots'. The other problem was of course that the block never acheived working temprature with all kinds of long term consequences for the bores and injectors, the latter needing much more frequent attention than their fw cooled counterparts. However they were very tough units, and kept on chugging away when many other makes would have given up the struggle.

Fresh water cooling makes a great deal of sense, and ensures a long trouble free life - at least for the engine!