Someone mentioned a facebook group it could be the gasket between power head and midsection letting exhaust gases mix with water? Inside where tstat is looked clear of buildup.
I did a compression test, however, it was a harbor freight kit. They all showed 90 psi, then 80 once warmed up. I returned that kit and need to buy a brand name and retest.
‘99 mercury 40 hp 2 stroke overheat alarm sounds after 5 mins of running. Has yet to sound when in gear WOT. Typically sounds only in idle after warmed up. Telltale has water coming out. I have replaced impeller (including housing/gaskets), tested and confirmed thermostat opens. Removed...
