I cannot figure out how to put the lower unit back to the motor after I
have removed the lower-unit to check the impeller. I inserted the
drive-shaft back to the hole and lined up the bolt; but I could not put
the lower unit all the way; something got stuck, and I ended up getting
a 1" gap that I could not close. I kept rotating the drive shaft
hoping that this might help the driveshaft to get on gear; but that
didn't help. At one point, I managed to get the gap to close to 1/2"
after spinning the driveshaft; but subsequent attempts of spinning the
driveshaft didn't help. By the way, the gear was at neutral if this
matters.

Am I missing something?

Thanks in advance for any help.

Jay Chan