You are not "missing" anything. Sometimes they just slip right in and sometimes they fight you. Remember: You are feeling for a hole (in the crank shaft) which is the size of the drive shaft-- not very big. Plus, the driveshaft is about 2 feet long and any tilt error on the lower unit is multiplied up top. And, the lower unit is heavy and difficult to hold. And then, to complicate matters, you also need to align the water tube and shift rod at the same time.
You need to insert the drive shaft as straight as possible into the mid leg and feel for the crank shaft. Then after fumbling around like a virgin and finally finding the hole, you either have someone turn the flywheel to engage the splines OR, with the lower unit in gear, turn the prop. Be certain that the water tube engages the adapter on the pump, the shift rod is in the hole in the mid leg, and have one bolt handy to hold the lower unit up while you install the others.
It may seem difficult the first time but after you have mounted a lower unit a couple of times it does get a bit easier and certainly, and extra set of hands ( even if it is only a 90 pound soaking wet woman) is a great help. Not dissing women, just saying that even the smallest can help.
