[Shadetree]

Just curious guys, as the designated caretaker of a 20cc i/o(120/140 Mercruiser w/ Alpha 1 Gen II drive) what kind of rpm do you all run when cruising. I was always under the impression that cast iron pushrod engines(NASCAR engines excepted)would not live long at high(over3000)rpm. I know a lot of boat owners that run thiers close to wide open a lot of the time(4000+rpm), and was wondering what kind of longevity one could expect under those duty cycles. I guess if it takes 5 years to rack up 500 hrs before a repower, it doesn't seem so bad. What is a realistic lifetime in hours for the average gas i/o powerplant? Or straight inboard, for that matter?
Pat in MD