Hey AST,
It's
funny how much is dictated by seasons up here (in Canada). Since
boats come out of the
water in Oct/Nov and consequently engines are decommissioned for
winter storage, often oil and filter changes are combined with the recommissioning in the Spring (or the decommissionning in the Fall). These are recreational sailboats, however, who do not put on a significant amount of engine hours seasonally.
Impellers are checked regularly by mechanics (again with seasonal de/re-commissioning), but only changed when they show wear or when the owner calls us with
overheating issues!
In an ideal world, boat owners would follow the manufacturer's specs, but overall, it does tend to fall to the individual boat owner's inclination to keep up their engine
maintenance (or not) as the case may be.
That's just what I've seen.
Good luck with your new boat! Wish I was motoring/sailing through the
ICW right about now!
Warmly,
LittleWing77