How many hours is too many on a motor

[Hammerhead]

I was told,...and believed'm that my '77 I/O had around 3000 hours on it. It ran fine and was only replaced due to a screw getting sucked down the carb and landing on a piston which blew a hole in the head. Otherwise it'd have about 4000 hours by now.

re;OBs,...I had a 20 year ld "115 "rude that ran strong till it caught fire and burned up,...while still running all the way across biscayne bay.