engine cooling

[Springer]

hi all,

 

I want to raw water cool my p2r, and i was wondering if it is possible to take the water from the prop access service hatch instead of fitting a conventional seacock ect set up?

 

would this be a problem?

[steamcompound]

In your position I would not. You will need a strum box or filter, and a stop valve on the inlet in order to be able to undertake maintenance or stop water ingress if a pipe gets damaged. The water in the area adjacent to the prop is very disturbed, possibly aerated and if the weed hatch cover has a lower plate flush with the hull exterior water flow may well be restricted. How about putting an inlet on the swim?

[BEngo]

I would not want to put a P2R onto raw water if I could put it on skin/keel cooling and use antifreeze. Raw water steadily and slowly dissolves the iron out of the cast iron, leaving behind a carbon matrix which looks fine, but has little strength. If your P2 has already been run in salt water as part of an earlier installation this will be well under way.

 

If a skin tank is too difficult then a matrix or snake of 1 inch steel piping can be welded to the swim on one or both sides. This is usually easier than a skin tank. About 4 lengths is fine on a standard swim. Inch piping has a surprising surface area for its length. 36ft of pipe happily looks after my J2's cooling on canal work though it does need a bit more for rivers.

 

The pipe does not seem to affect the handling and gets a pressure wash and a coat of black when the hull does.

 

 

N

[steamcompound]

The above is sound advice. 'Modern' raw water cooled engines (!gm10, DV10/20 etc) have sacrificial anodes in the water space which have to be regularly replaced. If you look at old marine engines which have been sea water cooled, erosion/rust is a major problem. Even Kelvin specifically excluded rusting in the water spaces.from their warranty.

 

If you want the reassuring sight of cooling water discharging from an outlet pipe on the hull then do the job safely, if being used at sea or in brackish water do not use brass fittings, they lose zinc, use marine grade alloys

[Bee]

A heat exchanger is best if it is possible, raw water through the heat exch. and engine and corrosion inhibitor / antifreeze through the other 'side' of the exch. If you do make a hole through the hull for the inlet then low down on the side is best for avoiding duckweed etc. mine is under the boat, seldom gets blocked but a devil to clear.

[Springer]

thanks guys, good advice.

[Dalslandia]

The skin tank, if fitting one, have to be 0.25 sq ft / HP (hp/4) the same goes for a pipe on the out side. ( My boat have 19 meter of 3" pipe)

 

1" is 3.14" around the inside. 3.9" on outside 1/8 thick. so need 9.25" -11.5" length per HP

Edited February 27, 2016 by Dalslandia

[Springer]

In your position I would not. You will need a strum box or filter, and a stop valve on the inlet in order to be able to undertake maintenance or stop water ingress if a pipe gets damaged. The water in the area adjacent to the prop is very disturbed, possibly aerated and if the weed hatch cover has a lower plate flush with the hull exterior water flow may well be restricted. How about putting an inlet on the swim?