He should do what I did when, long story short, my '5.0 Mercruiser engine had an issue in my 22' Sea Ray. I tried to have my local performance engine shop do some machine work on it and that wasn't going to happen until the boating season was over. He said "Mike I was just down at Summit Racing and sitting there for $2300 was a BRAND NEW GM Goodwrench 5.7/350 crate motor and for a few more bucks for a Melling new camshaft and some brass freeze plugs you will have a NEW motor. Plus there no telling what you get when you buy a used block or motor especially if it's out of another old boat. Go to Summit and buy a new GM Goodwrench 350 crate motor and change the cam and freeze plugs and use the boat intake manifold, fuel pump (I bought a new marine fuel pump) and use all of the other boat specific components. I picked up 65 hp too going to the 5.7.

Mike