Originally Posted by
jimandmandy
Sounds like similar operating cycle as aircraft engines, which operate at full power for takeoff and climb and almost full power in cruise. Also they have tight cowlings. Still, boats have unlimited water cooling available, so cylinder head temps have to be much lower. As with aviation, magazine articles and many mechanics perpetuate myths, which turn out not to be true. "Leaner is hotter. Richer is cooler" is the worst one that has finally been proven wrong with fully instrumented aircraft engines. I doubt if anyone has put CHT and EGT probes on every cylinder of a marine engine and adjusted the mixtures real time to see what really happens.
Jim
They do have unlimited water cooling but during the summer when water temps are nearing 85 degrees, the cooling efficiency drops off. Like you pointed out with aircraft engines, marine engines do have to operate at near full power to get on plane and still maintain most of that power at cruise. Also, take into affect that the water is no where clean, the cooling passages corrode over time due to impurities, especially in saltwater, and even get completely blocked in extreme cases causing hot spots. I'll agree that the valve seat issue is isolated, but has happened more so since ethanol has been introduced into fuel. They should put pyros in the exhaust to see if they really is an effect from ethanol or if it's a myth. I have a feeling, even with research, the cases will most likely still be isolated.