Chief, I'm 20 mins from Levittown PA. If I had known you were that close I would have bought you a cold one!
LTR 330 hp Indmar would be my guess. I'm sure you could get a direct replacement engine. Or you could try Jasper or ATK and see what they offer. www.part-man.com
sells Mercruiser engines I think.
Rep, that's bottom paint on her which will slow it down. You can soda blast it off and maybe save the original gelcoat finish.....it's a gamble, you won't know for sure until you try.
And yes zinc on the rudder, maybe on other places too (strut, tracking fins?) Salt kills.