Join Date: Jan 2007
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Rep Power: 9
Yanmar 2GM overheating
Ran my 25 year-old raw water cooled 2GM for about an hour, against 35 kt headwinds, and the water temp alarm came on. Don't have a tach, but I was trying not to push the engine too hard, and was only doing a couple of kts, into the wind/waves. Shut engine down, removed hose at exhaust elbow, and got a dry poof of smoke. Started the engine, and got water immediately - which was obviously hot. Put the sails up and let the engine cool for several hours. Ran again for a few minutes to get on mooring.
I will take the exhaust elbow off, to look for blockages, but as the engine was in salt water for 25 years, should I try to flush with oxalic or muratic acid. If so, do I need to take the thermosat off and use a drill-pump to circulate, or can I run the engine until warm, change the water intake hose to the acid bucket and run the engine for a couple of minutes - and let sit.
I have previously checked the impeller, which seems fine, and norammly, water flow seems normal. The exhaust / water exits underneath the stern, so you can't see the water flow from on board. I don't know if the was flow reduced, or stopped totally when it overheated.