I recently updated my '65 6hp Evinrude by replacing ignition parts and water pump. Last night I changed the pump and put in new gaskets around the housing. When it came time to reattach the lower unit, I was able to insert the drive shaft, attach the shift linkage, and hook up the water line. However, the lower unit will not go on all the way, it is about 1 inch apart and I have no idea what to do. I can shift between neutral and reverse but not forward in this position. Does anyone have any idea what is keeping the lower unit from sliding all the way on? The drive shaft should be all the way in the powerhead, when I turn the prop the crankshaft turns as well. I really appreciate any help.