Overheating problem - look for the simple things first

[Dutch01527]

My 1984 Dehler has an original Farymann 25hp engine which is a marinised Kubota 3 cylinder diesel. It has had a long standing tendency to overheat when used at full revs. Local marine engineer has looked at it and not fixed the problem. Next step suggested was change heat exchanger at a cost of about £1,000 if we could find one.

The engine runs fine at 75% revs but overheats above that. It was obvious there an issue somewhere within cooling system which is raw water. I decided to start at the sea cock and work my way through the system until I found the issue. Pulled pipe off the sea cock and opened the valve - big gush of water so that was not the issue. Pulled off the strainer which was fitted by the previous owner and it had the flow the wrong way around and it had a very fine mesh. Bit of research on the internet showed that the strainer was designed for fresh water electric pumps.

Changed it for a raw water, large mesh strainer from the local chandler at a cost of £9 and problem solved. I will replace it quickly with a better quality one as a safety precaution.

Very satisfying couple of hours work.

 

[Caraway]

Good on you. It was going to be a flow or efficiency problem.
Shame the engineer didn't follow your simple, logical steps.

 

[Sea-Fever]

I hope you didn't pay them.

 

[Concerto]

The first things to check with overheating, is there cooling water in the engine and is water coming out of the exhaust. If both look fine the it will most likely be a blocked water inlet, a blocked heat exchange unit or a faulty water pump/impellor. All of these should be DIY fixes. Only once these have been checked would I investigate further or call in an engineer.