Swapping a mercruiser 140 for a mercruiser 120

[Alloveragain]

Hello all.
Is there anything need to be aware of when taking my mercruiser 140 out and putting a mercruiser 120 in?
Are parts from the 140 possibly going to work on the 120. From what I have been reading they will. The only difference is horse power.
Any info would help on this topic. Also is the 165 mercruiser usable?
I know the difference is horse power but what I am asking is can all exterior parts work from engine to engine?
My 140 has a crack in the block from the last owners.
Thanks.

 

[Scott Danforth]

the 140 is a 3.0 liter motor, the 120 is a 2.5 liter.

there were two 165hp motors, the old inline 6 cylinder with 250 cubic inches, and the Mercruiser 3.7 liter 470 motor which has nothing in common with either of the other motors.

there were significant differences introduced in 1991 to the 2.5 and 3.0 motors, so as long as you keep your vintages the same, you should be able to unbolt the 3.0 and bolt the 2.5 in, then align and mount the drive

why not find a 3.0? plenty out there