I'm converting a 1961 Johnson FD15 18HP from long shaft to short shaft - basically just getting rid of the extension kit. The motor came with two beat up longshaft lowers, which I will turn into one good shortshaft lower. I can cut down the water tube easy enough, but I'm looking to get a good used shortshaft driveshaft. I don't have one to measure - just the longshafts that came with the motor.<br />A guy online has two likely candidates, both 4 spline top and 11 spline bottom, 1/2" diameter, pin for waterpump. One is 25 1/16" long and the other is 26 1/16" long. The 11 splines on the shorter one run up the shaft a bit farther, and end in a narrower groove, than on the longer one. I don't see that this would make any difference, though. The two long shafts that came with the motor have exactly the same difference he describes but are, of course both the same length.<br />Which of these two driveshafts are correct for my FD15? 25 1/2" or 26 1/2"? <br />My 1961 parts catalog lists the shaft as #303860, no length described. I'm told replacements are available from dealers for $240 - out of the question. I bought this motor for $100 to part out spares for my FD21, but now I just gotta bring it back to life. Thanks!<br />PS - I saw a different lower unit listed as fitting "both 15hp and 18hp, this one's set up for the 15HP". Do you suppose the 25 1/2" driveshaft is for a 15HP?
