Sea King 15 running hot

[auldscott]

I have a 1962 OMC-built Sea King 15. When I first had it, I ran it for a couple of hours total over three separate outings. All was well; it ran great. Last February I was running it for several hours with three aboard my boat, often at full throttle. No problem, until the second day of running when I noticed that the water discharge was getting hot, even at idle. Water volume seemed unchanged and still looked sufficient. Being several miles from the dock I nursed it back, and it never got dangerously hot (burnt paint) but the water discharge was almost painfully hot, as was the cylinder block. In addition, it would sometimes lose power, but still running on two cylinders and not four-cycling or lean sneezing. I replaced the water pump housing, plate, impeller, and seals. I ran it today and nothing has changed; still running hot and losing power. The new parts didn’t increase water flow out of the discharge opening.

I know it is difficult to diagnose such a problem at a distance, but perhaps someone has seen something similar. Anyone?

Thanks!

[frankr]

That cooling system is about as simple as it gets. My first suspicion is a piece of an old impeller lodged somewhere in the powerhead.

[auldscott]

Thanks, Frank. The impeller I took out was fine, but that’s certainly a possibility.
After that post, I checked the compression: 75 bottom, 90 top. Could a leaking head gasket contribute to running hot?

[frankr]

That is possible. But I suspect you have a far more fatal problem. The old lower crankshaft seal thing. Those seals were trouble makers. They allowed water to enter the crankcase, which destroyed everything. It’s time to pull the powerhead for an inspection of that seal.

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