Re: Can i put a 120HP Force powerhead on a 1991 90HP Force leg?
Depends upon the year of the powerhead.Up untill 94, they all were the same and used all the same components with the exception of the three cylinder trigger for the 90. SO if you are using an early Force powerhead, uyes, they are swappable. The 90 lower unit will provide more acceleration than the 120 lower and that includes going up 2 pitches in prop. I.E. If you are now using a 13 X 17 prop you will need to go up to a 13 X 19.
94 and later used Mercury control cables and I am not sure: The block itself will bolt up to the leg but the linkages may be different. They may also have changed the splines in the crankshaft.
Where are you located?