3.0L differences

[matt167]

I noticed while doing some maintenance that my new boats 3.0L has a fairly decent oil leak from the rear main, and I noticed doing plugs that #4 was severely oil fouled. I have a 1988 3.0L that is solid and mint running however my wife now wants to fix the boat that it’s in. It would be a direct swap as both boats are nearly identical with power plants being alpha gen 1 3.0L, 1988 and 1989 respectively.

What do I need to do to put a 1991 or later 3.0L in an Alpha gen 1?

 

[Scott06]

I noticed while doing some maintenance that my new boats 3.0L has a fairly decent oil leak from the rear main, and I noticed doing plugs that #4 was severely oil fouled. I have a 1988 3.0L that is solid and mint running however my wife now wants to fix the boat that it’s in. It would be a direct swap as both boats are nearly identical with power plants being alpha gen 1 3.0L, 1988 and 1989 respectively.

What do I need to do to put a 1991 or later 3.0L in an Alpha gen 1?

the difference is the flywheel size and coupler style. Older engines has 2 piece rms and 12 5/8" flywheel, later are one piece RMS and 14" flyhweel.

Earlier engines used a crank hub mounted coupler , later the three bolt (current) coupler that bolts to what would be pressure plate mounting holes in a automotive application.

If you have a complete bobtail you are swapping in I dont think you need to do anything except keep the flywheel coupler and maybe flywheel cover with the same generation engine. Only issue is if you have a bare long block and are mixing and matching parts. The input shaft for the drives is the same length alpha gen one and two. Real early MC1 (60-70s vintage) used a shorter input shaft on the drive for inline engines (2.5/3.0/165) , but thats not applicable here.

If you have a gen 2 drive/transom assy set up from your 91 and up 3.0 you can swap the whole thing over but I may be making more work for you ...

 

[matt167]

I’m simply thinking of finding the newest engine I can and dropping it in. Transom assembly is actually in good shape. I do have a good gen 2 transom assembly but it’s from a 4.3L and I don’t have rams or anything else for a gen 2. I have a good spare gen 1 Alpha and a spare MR1 drive that I think could fit…. For the time being I’m going to try jamming some pigmat up in there to get through the season.. I should not have sold my spare engines but I did.

 

[Scott Danforth]

1991, the block was changed, 1- piece RMS crank, moved all the tooling to Mexico, consolidated designs of rotating assembly with other GM motors

The flywheel went from a 153 tooth to 168 tooth

So get a complete bobtail

 

[Pmt133]

When dad repowered originally, we replaced a 1984 140 with a 2001 (or 2003, don't quite remember the year anymore as I was either 5 or 7) 3.0l crate. Aside from the engine harness plug being different (the new crate used a smaller what he called outboard style plug vs the large 9 pin I'm used to) and the shift linkage plate being on the side instead of on the valve cover, it bolted directly in no modifications needed even including the exhaust plumbing. Maybe the holes in the front mount were different and that was redrilled. Same length just narrower or wider.

If you have a complete engine it should be drop and go.

 

[matt167]

There is a mid 2000’s complete bobtail on marketplace at the moment. I’m debating looking at.

 

[Chris1956]

Gee, If you are going to swap engines, can't you pull the oil pan on the leaking engine after it is out and replace the seal? Just a guess.

 

[matt167]

Gee, If you are going to swap engines, can't you pull the oil pan on the leaking engine after it is out and replace the seal? Just a guess.

If that was all… of course. But #4 is also severely oil fouled and 1-3 were clean. It had a slight miss at idle which I fixed with new plugs but it’s going to happen again judging by #4. It runs decent now though.