The driveshaft tends to flop around in the drive shaft tube
making it a challenge to get it back into the hole of the
crankshaft however if you still have the water pump
installed the spring in the piston will force the driveshaft
to the side of the driveshaft tube. You should be able to
to move the crankshaft so the flange will bolt up to the block
It might be easier for you to remove the water pump as well
as the lower unit gears and install one part at a time.
Tubs
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.