Hi, I am new to this board, I am hoping someone can help me. I have a 1976 Mercury 9.8 long shaft outboard. My lower unit is toast so i was wondering what other years up or down in years would fit. Can a short shaft be used just by changing the mid section? Would a 7.5hp be the same? Someone has a late 60's long shaft lower unit from a 110(9.8) thats in pretty good shape, would that work? Please if anyone with knowledge of these lower units can tell me what I can use then I would know what to look for. Thankyou.
Yes, you can use a short shaft lower unit if you swap out the mid section to short shaft.
-I think you want a '75 and up lower unit. '75 driveshaft is a combination stainless wet end and carbon steel top end (splined to fit the crank). 76 and up is an all stainless drive shaft which is the best. 74 and lower will be a carbon steel drive shaft which rust and lose the seal face and so leak water (sooner).
-70 and below have carbon steel drive shafts (not the best) and have a reverse action shift mechanism vrs 71 and up. 71 and up have the same shifting action as your 76.
Even though the part numbers change, I believe any 75 and newer 9.8 or 7.5 lower unit will work.