Replacing 43 OMC

"My '91 4.3 OMC wasn't

"My '91 4.3 OMC wasn't winterized and the heads and block cracked. Didn't know this when I bought it, so, lesson learned. I need to know if a vehicle 4.3 engine can be used to replace it? Thanks for any help!!"

"yes, look for similar year, a

"yes, look for similar year, and preferably 1991... Astro Van, full size van, pickup truck best candidates

Need to get a 4.3 that has provision for mechanical fuel pump
Replace the tin core plugs with brass ones.

Then swap EVERYTHING over from the marine engine.
Ignition, fuel, electrical systems.

Your heads wouldn't be cracked, but the block would be, and you'll likely need new exhaust manifolds.
A purist might pull the truck engine's cylinder heads off to swap in composite gaskets, but if you boat in fresh water, not absolutely necessary."

"The heads were both cracked t

"The heads were both cracked too. I was in the process of replacing them, when I saw the crack in the block behind the push rods. If I can't find a '91, do you know what years I can look for? Also, here is another question. Is there any way to weld or JB Weld the crack in the block? I know this is pretty redneck, but maybe worth a try. It ran great before I noticed the water pouring in through a popped freeze plug."

"[i]Is there any way to weld o

"Is there any way to weld or JB Weld the crack in the block?

yes, and no

When ice broke the cast iron, it also shifted other things around in that casting. The 6 cylinders are not likely where they used to be anymore. An engine is a precision machine and who knows if your main bearing journals are in perfect alignment anymore. If this were some rare museum piece, but 4.3's are a dime a dozen.

Where did the heads crack? That's a very hard freeze. I would look closely at the intake manifold too then if water was that high in the engine when it froze. I have heard of that before, but of all the frozen engines I've disassembled, the heads have always been undamaged.

I wouldn't stray too far from 1991, but you can look for a mechanical fuel pump friendliness on any motor I suppose. "

"Hey Greg, If you can't fi

"Hey Greg, If you can't find a used engine,check with GM parts about a 4.3 long block crate engine or advance auto parts or autozone, i know they have reman. engines and may have a listing for marine engines. If you can't find the manual fuel pump block you could use a 5-7 psi inline electric fuel pump,just be sure and use a low oil pressure switch to shut the pump off if the motor ever shuts off or something happens.Very easy to set up."

"Greg, another thought, www. R

"Greg, another thought, www. RapidoMarine has true marine reman. engines avaliable at good prices with no core charge and flat rate shipping."

Thanks guys. You've given

Thanks guys. You've given me a lot of good info. Looks like I've got my winter project! I'll be checking into all these options. Hopefully it goes well. I'll be sure to write again if I run into anything more. Appreciate the help!

Another question. I found a bl

Another question. I found a block. Would there be any reason why I couldn't rebuild the engine using this new block and my old parts? I've read several places that the marine version of the 4.3 has 50 more horsepower than the vehicle version. What makes the difference and would swapping my parts keep the 50 HP. Does the block have anything to do with it? Thanks again - Greg

"[i]any reason why I couldn&#3

"any reason why I couldn't rebuild the engine using this new block and my old parts?

by definition, using "old parts" isn't rebuilding.

If there's any HP difference in the long block assembly, it would be in the cam.
I might swap the cam over and put new lifters, or order a marine cam and lifter set from Summit or similar if kits exist...

would depend on what the 4.3 came out of"