OMC Lower Unit Compatibility

[twister123]

Some of you may have seen this thread before. Well, I couldn't find the original. Anyways, I have a 115hp 1976 OMC with a blown LU. Now I'm in search of one. Are other years compatible with 1976 V4 motors? If not can I make small modifications to make them function?

[Paul Vaillancourt]

That motor is right in the period of transition. I think you are gonna need 1976 or older. The differences are in the shifting rod and water pump. The older I think 1976 or 1977 is when they changed, has two water outlets out of the pump up to the mid section. The older style shift rod bolts onto the intake manifold or block (can't remember) and the newer has a screw that is under the bottom carb.

[twister123]

So, If I change out the water pump and modify the shift linkage, can I get a newer 79-80's LU to work?

[Paul Vaillancourt]

I think that you will need the intake manifold that goes with the 79, use the shift rod that comes with the 79. I have never tried that conversion but I was thinking about trying to put a newer gear case on my 1973. When I started looking into how the shifting worked it seemed like that was the easiest way since I have the intake that goes with the lower unit. And I was gonna use the older water pump housing.

[Da Bull]

Ya better check first but I don`t think the 77 and newer has the same bolt pattern as the 76 and older. The 76 and older gear casses are not as long from front ta rear
as the 77 and up.

DB

[Paul Vaillancourt]

That is one thing that I didn't check!

[Riverratt]

I have a 1978 85hp and it has the newer shift linkage with the bolt under the carbs

[twister123]

I will compare the footprints for each.