How many hours is too many on a motor

[Steplift 72']

Originally Posted by Blue_Runner

Step, don't you mean under-propping? If not, what is it about over-propping? I've heard underpropping causes the motor to work harder, which makes perfect sense to me but I don't think I've heard of over-propping??

By overpropping, I mean too much pitch. Back in the late 70's I had a dealer sell me a 115 with a 19" prop. It managed to make just over 5000 rpm at WOT with a light load. The recommended range was 5000 to 5500 rpm. Loaded it ran 5000 rpm and accelerated slowly. By 250 hours it barely made 4900 rpm and had lost a few pounds of cranking compression on #1 cylinder. Later, a local dealer told me that he'd rather see an outboard slightly over the maximum end of the rpm range. His point of view was that he'd repaired many more motors being lugged than over revved.

My 1986 248 Offshore was propped to turn 6000 rpm with a full load and I sold it running well with over 2000 hours.