You'll want to do a mechanical survey or engine inspection on any used
boat.

It could be a mistake to assume that any gas engine with just a few
hundred hours on it must be in good mechanical condition. It doesn't
take too many hundred hours of neglect and abuse to destroy an engine.

It could also be a mistake to just write off boats with over 1000 hours
as unworthy of inspection or consideration.

The guys who really take special care of gas engines, and have a
moderate amount of good luck, often manage to get 2000 hours service
before major overhaul or replacement.......but not always. You'll hear
of cases where the engine lasted a good deal longer, but the reason
those stories make the rounds is because that sort of longevity is
atypical.

Once past 1200-1500 hours, most people begin to consider a gas engine
thoroughly used, if not used up.
Hopefully, the seller of the boat will have priced the vessel
accordingly.

In the end, the only variable that matters is the shape of the engine
in the boat that *you* want to buy, and that can't be determined by
hours alone. Just don't pay a premium price for a gas engine boat with
hours in the middle teens, even if it is running OK when you buy it.
Nobody expects a 65 year old man that the doctor pronounces "in perfect
health" to outlive a 35 year old receiving the same evaluation. :-)