TanzerTom, it all comes down to care and use. When buying
an older boat, the engine
is pretty much a black box unless you can have a high level of confidence, for one reason or another, in how well it has been maintained and run.
So you can basically forget the hour meter. I've seen engines destroyed in under 1,000 hours due to poor maintenance
and neglect, and others at 10,000 hours that run and operate as new.
Any "average" is only that, and it's worthless with respect to evaluating the lifespan of the engine
in a prospective purchase