i did one like that a while ago, but before you pull it down, check the shift linkage behind the water pickup, pull the threaded coupler apart and inspect the plastic grommets(couln't think of a better discription). make sure they arnet worn, while you have the coupler aprt, try to shift the unit at the gear case by moving the short rod while turning the propshaft, if you can get it in gear both ways, you r problem may be else where