Yanmar Overheating

[Ward Niffenegger]

My 1GM10 Yanmar overheated when I used the boat for the first time this year. I found the hose barbs leaving the water pump and the hose barbs on the thermostat to be blocked. I reamed them with a small screwdriver and everything is fine.My question is should I boil the block or treat it in some way to clean crud from the inside of the engine. The engine is raw water cooled and is now a fresh water boat although it spent several years in salt water. The blockage looked like lime, but could have been salt.Thanks for the inputWard

 

[Steve O.]

cooling system

Yanmar engines use raw water to cool the exhaust gas only. You could have a clogged intake strainer, worn or broken impellor, or blocked mixing elbow. The first two are easy to fix, mixing elbow is more difficult. Search the archives for this if you determine that is the cause.The engine block is cooled by a closed system of coolant/anti freeze. I would suggest flushing and replacing the coolant, including the heat exchanger (if you have one).

 

[Ward Niffenegger]

Thanks for the input Steve BUT

The 1gm10 has no antifreeze and is not a closed system. It draws raw water from the lake or ocean and runs it through the engine block to cool. My problem is lime or salt built up inside the engine block. I am wanting to know what the proper procedure is for boiling out my engine block. What chemicals should I use (if any).ThanksWard

 

[NYSail]

In mine

My Yanmar, a 3HM35F the sea water cools the engine and exits into the exhaust system. I also have anti-freeze, however if you stop the flow of seawater, the engine will overheat...the sea water disipates the heat of the block.....there is no need to cool the exhaust gases exclusively.In my manual, it tells in detail how to clean the engine.....There are parts to remove that expose the tubes, however mine is different and does not circulate through the block as yours does. Good luckGreg