I found 19433158 short block in stock. It's not cheap, but I think that it is the best one.
Boat is 42' Harley. Used mostly offshore. Cruise RPM is anywhere from 3400 to
3900 depending how heavy we are loaded. Has anyone used one of these? Was is trouble free?

Thanks,

Steve

502 is a great platform to build on, make sure the block isn't beat up and cylinder walls are sonically tested for good thickness. The bigger question is going to be what type of build are you wanting? I don't boat at sea level but I'm betting you need more power than what the stock 502 came with since you're you got bigger boat. Are you single or dual motor? the 502 came in two variations if memory serves me....415hp and 475hp respectively. If you're a single motor boat you will need more power imo.

Steve, that’s a factory Gen VI 502 short block with a GM 502/502 cam and truck oil pan. It will need a cam change, oil pan change, brass freeze plugs (if not already there), and the oil bypass valves swapped out.