Replaced the water pump impeller on my 1990 5 HP 2 stroke and that went smoothly. When I went to re-attach the lower unit, hooked up the linkage no-problem and inserted the drive shaft into the engine where it would turn then motor over but still needs to go up another inch to insert the bolts and tighten down? It's like the drive shaft is an inch too long. None of the Youtube vids that I've been trying to self educate myself with seem to address this issue. Any ideas would be of great help.