Re: 125 hp lower unit fit a 90hp?
We really need to know the year of the lower units. If they are the same it should work.
Count the number of splines on the shaft, it will be either 13 or 15 and check the length of the shaft that will either be 15" short shaft, 20" standard shaft or 25" long shaft. If this is all the same and the bolt patterns are the same they should be interchangeable. The gear ratio might be different in the two units and that would affect the RPM's on the motor. But thats fixed with a different prop pitch.
