gunge

[nac]

I have a beta 20hp diesel inboard , and on inspection of heat exchanger I found it to be stuffed with green gunge. I cleaned it out with a fine piece of wire and it seems ok now. Has anyone else had this problem, and whats the cure.
nick.

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[Evadne]

The green colourprobably comes from the copper, was the gunge a sort of mushy, gritty substance and was in the salt water side? Do you have an internal anode in the heat exchanger? I get that sort of thing on my raw water cooled engine with an internal anode due to leaving salt water in the system when its not running. The anode quietly goes on corroding, leaving zinc salts to accumulate on other surfaces. The answer is to drain the salt water off when unused (especially over the winter). A recent thread on "Yanmar overheating" recommended antifreeze for dissolving this, I intend to try it this winter.

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