Join Date: Oct 2010
Thanked 47 Times in 46 Posts
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Re: Raw Water Cooled for 35 Years?
My engine is a 1980 Yanmar 3gmd (raw water cooled). I also depend on it to get into and out of harbor safely. Was also concerned about engine when I purchased boat. I did go through the cooling system (repalced raw water impeller, all hoses, inspected strainer, replace thermostat, carry spare raw water pump, replaced engine zincs).
I also flush the engine with fresh water on return to dock. For this get a bucket and install a hose fitting at the base that you can run your engines sea water pump suction line to. When you return to dock cool the engine down by using fresh water. Always let engine pump the water- you do not want to hook pressure hose direct to the engine- might cause damage.
One sailor I know uses salt away to flush. He leaves it in the engine between uses. I am on the fence on this.
I have looked into my engine block and do not see corrosion. One mechanic told be these engine used good materials and things like zinc protection and they will last. The thing I like about the direct sea water cooled is they are much simpler than a fresh wate cooed. The direct sea water has one less water pump to fail and does not have a heat exchanger to deal with.
A replacement engine for a 20 hp is going to cost around $11,000 and say another $5k for install when all said and done (boat yard install with potential engine bed mods). May or may not be more reliable than what you have. The way I see it, anything can break.