gearcases from '80 100hp Johnson compatible with '92 90hp Johnson?

[skip17ff]

I've found a lot of mixed literature on this. Some say the lowers for the V4s are interchangeable from 1978-1998. I got a rebuilt 1992 V4 90hp Johnson lower to put on my 1980 V4 100hp Johnson. Everything is identical except the driveshafts.

I know they switched to a 2 part shaft. This lower bolts right up no problem. But now that it's married my motor struggles to crank. I put some dish soap in the impeller housing before I installed the lower. This lower may have sat for a year or 2. I was able to hand spin the driveshaft before install, but with some muscle.

Is this a total waste of time or do I need to just get this spinning and let the impeller losen up?

 

[havoc_squad]

I am assuming you actually bought a v4 90 degree crossflow lower unit made in 1992 and not a late 90's OMC 90hp v4 60 degree looper one.

If you can hand turn the vertical shaft with the impeller, you should be able to install it.

Have you verified the shift shaft is the exact shape, not bent, and the correct OEM manual length for your outboard?

If that is not correct, the lower could be attempting to shift in neutral, which does cause binding/excessive starting load.

 

[racerone]

There you have it.-----When you install the replacement lower unit the driveshaft does not fit properly and JAMS up the crankshaft !!!!------Get help from someone who knows this stuff.

 

[havoc_squad]

Let me guess, I probably somehow missed some critical info about drive shaft length difference of the single piece shaft versus two piece shaft.

A brief confirmation of this as fact by racerone or joe reeves would be appreciated.

I don't mind correcting myself if wrong.

 

[racerone]

Not really the overall length.-----It has to do with the SPLINE ARRAGEMENT and the way that fits into the spline on the crankshaft.-----Skip has to contact a the seller or talk to his friendly local outboard shop !!

 

[havoc_squad]

Basically a problem similiar to an I/O outdrive gimble drive shaft being badly out of alignment into the engine coupler and causing all sorts of wierd engine issues and noise.

That would be a very bad problem if that vertical shaft is bent or splines goobered up.

 

[skip17ff]

Sorry for the delay in response. Yes I had to swap out the upper driveshaft to the correct spline style. OMC had 3 versions of shafts for the v4 crossflows. The lowers are otherwise interchangeable. This lower came with v2 and I need v1. That gets delivered today.

The shaft spin issue was completely contributed to the water pump. I got a new one to install with the new shaft.

 

[racerone]

The water pump has nothing to do with it.