Motor swaps

[Kewen3001]

I'm sure this has been addressed many times, I currently have a 1987 mercruiser 4.3 alpha 1 gen 1. I'm having some. If issues with it. I'm wondering is it possible to swap out with a automotive gm 4.3?

What is the difference (besides gaskets/exhaust manifolds)

Also if I needed to would I be able to drop a 3.0 4cyl motor in and have it fit the same with the outdrive?
Thank you

 

[nola mike]

Yes, you can swap an auto block, swap over your accessories, change head gasket and core plugs and call it a day. You'd need the same vintage block (non balance shaft, pre vortec--i think the cutoff would be pre-1992). Or you could upgrade to a balance shaft vortec engine, doable but more work. In addition to being a huge decrease in power, you'd need new mounts (and I think the 3.0 is longer as well), probably a new out drive (different ratio), and ALL the accessories. OR you could put in a v-8.

 

[Kewen3001]

Yes, you can swap an auto block, swap over your accessories, change head gasket and core plugs and call it a day. You'd need the same vintage block (non balance shaft, pre vortec--i think the cutoff would be pre-1992). Or you could upgrade to a balance shaft vortec engine, doable but more work. In addition to being a huge decrease in power, you'd need new mounts (and I think the 3.0 is longer as well), probably a new out drive (different ratio), and ALL the accessories. OR you could put in a v-8.

Are the heads the same? Would the auto head have the same bolt pattern for the exhaust manifolds as the marine?

 

[nola mike]

Are the heads the same? Would the auto head have the same bolt pattern for the exhaust manifolds as the marine?

Your heads will fit a pre vortec, exhaust manifolds are the same and will fit a vortec long block

 

[Kewen3001]

Your heads will fit a pre vortec, exhaust manifolds are the same and will fit a vortec long block

But will the auto heads(pre vortec) fit the (prevortec) marine exhaust? Wondering incase I find a clean motor and decide not to change gaskets right away.

 

[nola mike]

But will the auto heads(pre vortec) fit the (prevortec) marine exhaust? Wondering incase I find a clean motor and decide not to change gaskets right away.

Yes

 

[Scott Danforth]

Block, heads and crank do not know if they are in a boat, a truck, a car, a genset or a forklift. However the whole longblock does. Cam, gaskets, core plugs, accessories, electrics and industion are marine specific

Dont even think of bolting the motor in the boat until you change the core plugs, head gaskets and the circulating pump. Those are matine specific for a reason. Also, if you dont swap to a marine cam, make sure you get a truck engine. The cam profile of a car has too little lobe separation