Muscongus, the answer really depends on a lot of variables, such as
Have you experience doing a gasoline engine rebuild
? Are you a competent amateur mechanic
? Can you personally assess whether all you need to do at the moment is reseat the exhaust
valve where the seawater came in? Am I writing Greek to you?
Seriously, it has to do with skill level, willingness to tackle a new project
(which involves time and money), personal preferences (I have more money
than time, I know a good honest mechanic in my area, etc.)
That's an old engine, with some peculiarities, but it's pretty easy to work on. On another thread, we have Sailorchick, who is tearing down an engine even as we write, it's called something like, "I got bored, so I pulled the head
on my engine." She's getting lots of help.
If the engine is trashed, you may not want to fool with it. It's a really old design. Others will undoubtedly tout to you the virtues of a new engine; but you are the only one who knows what your resources and preferences are.
Good luck with it.