I was wondering what I would have to do to put a 87 EFI 350 engine into a boat that had gm motor?

Question

engine out of 1987 chevy blazer boat is a 1989 baja 21ft that had 454

Answer 1

Your biggest issue is to replicate the inputs required for your EFI to run properly. 87 is pretty early and basic but it still required many external sensors to properly meter the fuel.

Answer 2

You would need the correct water cooled exhaust manifolds (which won't swap over from a big block), exposion proof starter, distributor, and alternator. No, the Blazer's EFI system is not marine approved, rest assured. The coast guard would smack you if they caught you, which would be better than going up in a fireball.

Please don't try it unless you have all the small block marine parts from a donor marine engine. Internally, the 350 block is the same as marine, but everything outside is different.