Will a 99 model 3.0 swap with a 77 model 3.0?

[Bigreddodge]

Hey guys just purchased a 1977 Thompson with an inboard OMC version of the mercruiser 3.0 but it’s the same As the merc engine just has omc decals. I have a 1999 Bayliner parts boat with a 3.0 engine in it that runs good. I was wondering if The engine in the Bayliner would basically swap in the 77 model when the 77 engine gets tired. I know the intake/exhaust manifold is shaped a little different but I’m hoping that the 77 intake/exhaust manifold would bolt on to the 99 head, And that the 77 fly wheel will bolt up to the 99 model.

 

[fastjeff]

It's a good bet. Both companies bought the long blocks from GM.

Jeff

PS: The late Dr. Strang first saw this motor in a Chevy II and thought it would work great in the new Mercruiser setup (he secretly invented). So he went to GM, bought a motor, and shipped it to Fond du Lac as cargo in Carl's private plane!

 

[Dieter]

Flywheels and engine coupler need change out - will definitely be different as later 3.0 is a one piece rear seal. See this advertisement for 3.0 at the bottom there are details about getting late model 12.75” flywheel and coupler.
https://www.michiganmotorz.com/base...nt-replacement-distributorno-coil-p-4531.html

i think you will also find the ports on the heads to be different as somewhere around 1990 they modified the head. Why not just use the manifold off the later one? Either way there may be some fit up issues or water / exhaust connection modifications required