I,m having a heck of a time trying to put my pre-alpha or R type mercruiser lower unit back on. I can't seem to get it in gear. The book says and everyone has told me to turn the shift shaft clockwise and the prop will lock in drive and will not spin clockwise therefore putting it in forward gear. BUT I can't do it, the shift shaft will only turn so far either way and I don't want to be too forcefull but it will not go. Now I can turn the shift shaft Counterclockwise and get the prop to lock in the clockwise direction but I'm told this is reverse and have installed it that way and it will not shift into forward gear. What am I doing wrong?