You will get a gambit of opinions on this one . . . so here is mine:
800 hours is a little on the high side, but manageable, if the engine has been treated well.
So, as you buy a boat with 800 engine hours, you would want to know a lot about the engine . . . compression test and cylinder leak test.
Also, you might expect that as you got up towards, say 1200 hours, you would be pretty close to a rebuild or some other major maintenance.
So should a well maintained boat be able to run 2500 hrs?
Generally, no, because a boat engine is working a lot harder throughout its life than a car or truck engine. So, the wear on internal parts will be higher. It is not an exact science, but a well maintained boat should go over 1200 hours.
If that was the case, why do the commerical guys get 3-4K hours out of a motor?
The fact is that most boat motors die a premature death from not being run regularly and or bad fuel maintenance. Very few if any are actally worn out.
I put over 2000 hours on my last three motors. The motor I replaced last Spring had 2260 hours on it. I know two people with close to 3000 hours on Yamaha F225s.
A Truck with 800 hours, run 100% of the time at 60 miles per hour, would have 48,000 miles on it.
Now, you could consider that a Trucks average speed is more like 30mph so that 800 hours is more like 24,000 Truck miles.
And if you grant that the boat boat engine worked harder for the 800 hours if it spent most of the time at WOT.
So 800 boat hours is more like 36,000(x1.5) to 72,000(x3) Truck miles.
Lets call it (x2) and we're back to the 48,000 Truck miles again.
Whoa, Uncle Willie ... is that a European Truck, or an African Truck?