I have a 1982 35 Hp 20 inch shaft that was suppose to be running great. So I mod the Jack Plate with Tilt that I make so the 20 inch shaft would work on my Gheenoe that the transom is made for a 15 inch shaft. It sounds great but has a bad clutch dog and maybe bad gears. I also have a 1991 25 Hp 15 inch shaft that runs ok but may need to be rebuilt soon. And I have a 2001 25 Hp 15 inch shaft that has a bad power head. What I like to do is to swap the 1982 35 Hp Power Head in to the 2001 25 Hp chassis, and keep the 1991 25Hp as a spare. If I can't do that can I swap the gear cases between the 1991 or the 2001 25 Hp with the 1982 35Hp? Before Jack Plate mod:1991 25Hp with a 3x10x12 Al prop: After mod: 1982 35Hp with a 3x10x15 SS prop.