1980 md7a 2 cylinder volvo diesel
. Raw water
. Since I have owned the boat (8 months) It has always run very cool. Less then 1/4 of the guage at all times I normaly cruise
at about 2000 rpms . Last weekend while coming in fighting a 25kt wind
on the nose and a falling tide, engine
at 2250. It sudddeny and instantly pegged hot and shut down. Dropped anchor
and checked the basics. Impeller = ok water
to impreller ok . Replaced impeller just beacuse I was there. Motor
cooled off started right up took the boat home at slow pace. Pulled the exhaust
manifold off and found some crud in the passages, found one small passage
in the head
blocked it appears to be the bypass for the water
from the cylinders around thethermostat to the exhaust
.Cleaned the passages in the head
and the manifold. Really wasnt much blockage except the one passage
. After cleaning
water from the hose flows freely though the manifold and and the head.
I did find that there was no thermostat installed. I installed a thermostat and the cleaned mainfold today and was supprised to find that at idle at the dock
it ran up the temperature to the line between green and red.
Theres 2-3 times the amount of water coming out the exhuast as there was before my cleaning
. I cant come up with any reason I could have good flow, good volume and still run hot.
Heres what I figure my options are.
New thermostat bad, could happen but I dont belive it
or the wrong temp sensor in the manifold.
Am I missing anything?
The tstat housing is warm but not hot to the touch and the exhuast water is warm not hot.