As much as I like the Chevy small block family of engines, at my age (68) there is no way I'd buy another I/O boat. I'm not against repowering the old one but if I had to sell this one, and was buying another, I just don't want to have all that work to do, every season. In salt water you're in the worst environment for an I/O, closed cooling is a big advantage, but still you have to maintain the transom mount and drive system.
Outboards are very expensive for the power they have but there are so many advantages, that can't be overlooked:
NO hyper expensive cat converter exhaust, if you are in salt water, it is a very big issue
Easier winterizing
Easier normal maintenance for oil changes and tune ups
simpler drive system, no complex transom mount, ujoints and gimble bearing, and bellows that can leak, and ruin the ujoints and gimble bearing
Better performance due to less weight
Safer, due to no risk of igniting fumes in the bilge
However, anything other than minor repairs will be expensive because not much aftermarket is out there for modern outboards.
You're not doing a top end overhaul by picking up a set of small block Chevy heads like I did at the local speed shop.
And in salt use, eventually the mating surfaces of the cyl heads and block get so corroded that you get head gasket leaks.
A closed cooled inboard, if properly maintained can last longer than an outboard, even in salt water.
