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 ...
