I purchased a Merc 9.8 circa 1984-5 a while back. The motor appears to be in
prestine condition. As a precaution, I changed the water pump impeller. I
just test ran it in a tank. No water came out of the tell tail; I undid the
thermostat housing and water + exhaust gushed out of the thermostat hole. I
found that the tell tale fitting that passes throught the body to be blocked
with what appeared to be a factory aluminum plug, I had to drill it out. Now
quite hot water and exhaust spits out of the tell tail. There was no
thermostat installed but schematics from the Parts Express site shows one. I
plan to install a thermostat shortly but cant figure why exhaust is coming
back through the cooling circuit. The motor runs well and has 90 PSI
compression in each cylinder, it looks new.
Any comments are appreciated.