Yanmar 1GM Flushing

[TDudley]

I need some advice on how to completely flush the raw water cooling system on my 1 GM Yanmar. I have replaced every part of the cooling system and still feel like I need to flush the system within an inch of its life. I keep having overheating problems. I need to wash every foul thing that has been sucked into it for the almost 30 years of its existence.

I am thinking a forward flushing and a reverse flushing. I am also thinking of using some type of flushing fluid. But I don’t what to hurt him (The boat is a she and I don’t yell at or talk trash about her. The engine is a he and we have had fist fights, but we still love one another).

Give me some advise please. No namby pamby stuff. I need the real deal. As long as I don’t have to take the engine or boat out. Been there, done that.

Thanks,

 

[Sailm8]

I had overheating problems for 2 years. Turned out to be a blown head gasket. I flushed with a descaler I found on line for boilers. You made a closed loop to flush it through the engine watching the temperature. Reverse flush is a no no as I understand it. You run the risk of forming a water lock in the cylinders.

Sorry I don't have the name of the stuff I used but it was advertised as used by the Navy and I had to pay a little extra since it was a hazmat item. Found it through google.

I'm sure you already checked for pieces of an old impeller and the thermostat is in correctly and working. Like I said I messed with all of this for 2 years before I hired a mechanic who found the blown head gasket. When he had the head off he reamed out the crap he found in the cavities.

 

[Benny]

It may be easier and more effective to clean out the cooling passages of the 1GM than to flush it. Just take off and replace all the hoses, remove the thermostat and get a small bottle brush into the head and engine block openings. Most of the debri in there will be sea grass, junk and perhaps pieces of a torn impeller. Don't forget to clean the thru-hull intake strainer. If overheating persists chances are the the problem will lie someplace else. Bad Thermostat, clogged mixing elbow, blown head gasket, leaks or impeller problems. Diagnose and repair.