Okay, that's good to know about the gear ratio. Unfortunately I can't swap the drive shafts, they're too different. Do you think I should have a notch cut for an O ring on the 18 drive shaft to match the 20, or does it matter?
I recently picked up a 1990 Mercury 20 hp. motor and it's in really good shape but the lower unit is junk (was run with no oil in it). I have a 1983 Mercury 18 hp lower unit that is in mint shape. The 18 hp lower unit had different size bolt holes to hold the lower unit onto the motor, was able...
