Algae on head and gasket causing overheating

[kenmon]

I purchased a 1999 Angler about 3 years ago with a 1999 Yamaha 115hp (C115TXRX) that was having a problem overheating above 3500 RPM. After changing the impeller, sensor, and finally the head gasket, the problem cleared. The port side head gasket had a moss or algae on it reducing its thermo conductivity. I changed the gasket about 16 months ago but the problem has resurfaced on the same head. I changed both head gaskets this time and the starbord side was fine.

I'm stumped! Has anyone experienced this problem and if so, what can I do to keep this from happening?

Thanks,

Ken

 

[WillyBWright]

Re: Algae on head and gasket causing overheating

Not algae, minerals. They lime-up over time. What I do is remove the head and lay it flat on it's back. Then fill the water jacket with vinegar and let sit overnight. That takes care of the head, but there's more in the block. You can probably scrape most of that off.

 

[kenmon]

Re: Algae on head and gasket causing overheating

But it's slimy, green, looks like moss.....still minerals? Why only on one head?