There is a technique in the service guides for installing the lower section.
You must make sure the shifter is in forward and the drive is in forward.
You need to use the prop to hold it all the way in forward while you slide
it up. By trying to turn the prop against the gears you keep it completely
meshed. It's almost a two person job.

"Johnny Miller in Hawaii" wrote in message
om...
I just dropped the lower unit of my Alfa 1 stern drive on a 1990
Bayliner Capri 22 and followed all the instructions to change a bad
impellor, left the throttle in forward. Then when I put it back
together the throttle would not go to reverse. Called a local boat
shop and they told me the shift spline was prob one tooth off and to
drop it again and turn it one tooth. Did that and throttle worked
fine. Started the boat out of the water and now the prop turns
clockwise no matter what position the throttle is in. Slower in
neutral, faster in forward and reverse. I can hand turn the prop
clockwise and it clicks in that direction but now counter clockwise.
What gives?? Thanks!