I'm putting the lower unit back on and for some reason it doesn't want to go on the final 1/4". The shift shaft slid in place nicely and I double checked shifting gears with the shifter with the appropriate prop action. I'm assuming I have the drive shaft splines lined up or I don't think I would have gotten this far in, and moving the flywheel causes the prop to spin. Is there some sort of pre-load pin at the top where the top of the driveshaft mates? I'm very wary of breaking something and thinking maybe I need to drop the LU and try again?