My 80 Century with the 305 Chev Mercruiser which I've owned only for 1 season, had a major overheat crisis late in the season. After wide open cruising for about 4 miles the engine was very hot. It was a bad time to discover that the back side of the engine was coated with oil from a leaky VC gasket. Fortunately no fire. I replaced the outdrive impeller which reestablished water flow through the outdrive and assumed i was done. When river testing the boat however it overheated again after about 4 miles of wide open operation. I was able to operate the boat at up to about 2/3 throttle without overheating. On advise from a forum, I am replacing the risers. So far, I've removed the port side riser, and may have found my problem. With the exception of two small drill holes, the gasket is completely restricted over the water ports.
I understand there are circumstances where this may be needed, but since my boat is operated in freshwater and the cooling system is not closed, what other than sheer ignorance would be the reason for doing this?
I don't know much about the flow of these systems. Please advise how this would work at all. Does the water that would normally flow through this manifold flow out through the other side unless the volume (high speed) is too high? It did seem that the port side was hotter than the starboard when overheated. I don't yet know if the starboard side has the same config but I assume it wouldn't work at all if it did.
I understand there are circumstances where this may be needed, but since my boat is operated in freshwater and the cooling system is not closed, what other than sheer ignorance would be the reason for doing this?
I don't know much about the flow of these systems. Please advise how this would work at all. Does the water that would normally flow through this manifold flow out through the other side unless the volume (high speed) is too high? It did seem that the port side was hotter than the starboard when overheated. I don't yet know if the starboard side has the same config but I assume it wouldn't work at all if it did.
