Swapping Internals From Marine to Auto Block (piston rings, bore size questions, etc)

[11b330i]

Hey guys!

So i have a boat with a cracked block. 1986 OMC 4.3 Cobra in it.

It has the 2pc main rear engine.

I purchased a donor 4.3 longblock from 1985 from a GM Van/Truck.

The internals and everything on the donor 4.3 are shot.

Would i be able to swap all my engine internals from the OEM OMC engine into the new block? This is where i am wondering about what parts to purchase. I want to replace the rings when swapping the pistons into the donor Block. Are the rings the same for auto and marine applications? I have found rings at the local NAPA but for the GM engine not the OMC (using their search function, which isn't the best).

Has anyone else done this type of swap before? I am confident in swapping all the head, cam , crank , etc ... Just need to know what parts i can use.

Thanks a bunch!

 

[Lou C]

The only way you can do that is to measure everything, or take it to a machine shop and have them do it for you. It depends on the wear in the donor block vs the components from your cracked block. Likely is that you need an oversize bore oversized pistons & rings, who knows what else. I personally don't have the patience for these projects, they can only be completed with a competent and cooperative machine shop. You're not piecing this together in your garage taking guesses and winding up with a good running engine....its all old stuff, with wear....