Usangi
Active Member
We've got an old Volvo Penta MD6A which is running hot at higher revs, and is stopping us going over 2-3 knots under engine. It also seemed like not enough water was coming out of the exhaust. I checked the inlet and that all seemed fine. As access is poor in my boat, and because I wanted to do a thorough check of the cooling system, I ended up pulling off the whole exhaust manifold. As a minimum, when I put it back together, I'll put a new impeller (and gasket and lubricant), and spin the cover around (as a little groove on it).
But I found some issues that I wondered if some of you more experienced people might be able to help with.
Missing thermostat - no thermostat was there when I opened this up. Turns out that is not completely abnormal - my friend's old boat engine also had a missing thermostat but doesn't overheat. Could it be a reason for overheating for mine though? And should I buy a new thermostat?
Blocked channels
On the photos, 1a and 1b are the two ends of a channel - both are blocked with rust or something. But what is strange is that 1c on the thermostat housing is blocked with some red rubber. Assume somebody has done that purposively? Anyone know what is going on here? Something to do with the missing thermostat? But the channel its blocking is blocked anyway with rust/crud.
Also 2 is blocked.
Should I just bathe the whole thing in some sort of acid/cleaner and see if that unblocks the channels?
I can't get the exhaust elbow off as one bolt is too tight on. But I've poked about a bit and it seems not to be blocked.
I don't want to spend huge amounts of money on this engine, but would like to at least try to get it running at a proper temperature. Any other suggestions on what to do?
But I found some issues that I wondered if some of you more experienced people might be able to help with.
Missing thermostat - no thermostat was there when I opened this up. Turns out that is not completely abnormal - my friend's old boat engine also had a missing thermostat but doesn't overheat. Could it be a reason for overheating for mine though? And should I buy a new thermostat?
Blocked channels
On the photos, 1a and 1b are the two ends of a channel - both are blocked with rust or something. But what is strange is that 1c on the thermostat housing is blocked with some red rubber. Assume somebody has done that purposively? Anyone know what is going on here? Something to do with the missing thermostat? But the channel its blocking is blocked anyway with rust/crud.
Also 2 is blocked.
Should I just bathe the whole thing in some sort of acid/cleaner and see if that unblocks the channels?
I can't get the exhaust elbow off as one bolt is too tight on. But I've poked about a bit and it seems not to be blocked.
I don't want to spend huge amounts of money on this engine, but would like to at least try to get it running at a proper temperature. Any other suggestions on what to do?
