1999 100Hp Yamaha Outboard Lower Unit Problem

[Alumacraft]

Hello,
I own a 1999 100hp Yamaha 4 stroke engine and last season I've gotten my lower unit stolen off the thing. So I purchased a very lightly used one for it. I'm having trouble fitting the main drive shaft in (It's the correct length). Everything slides in fine except that it sticks out about a inch and wont go any further. Im guessing it is the Splines. I cant seem to get them to fit, I turned the lower unit into gear and it wouldnt fit and in neutral it doesn't fit. PLEASE help, I want my boat on the water ASAP.

P.S. I'm kind of a newbie to the lower unit installation process, my brother would always do the impeller changes on it and stuff.

[rodbolt17]

sounds like the splines are not ilning up with the splines on the oil pump and the crankshaft.

[99yam40]

Try rotating the flywheel some to get them to line up or the prop with it in gear while installing

[rodbolt17]

the oil pump is mounted on the powerhead adapter and has internal splines,the crankshaft internal splines are on the crank.
however both sets of splines have to line up.
are you positive you have the correct gearcase?
the two stroke case looks similar but the shaft splines are to short.