I just bought a 1994 Four Winns with a 4.3 Cobra drive. There was no prop on it so he grabbed on from a small stack he had in storage. A couple of them fit but would not seat all the way down, leaving a gap of 3 or so inches between the prop and the outdrive. Since none really seemed to fit, he gave me $100 to buy a used one that does. I happened to have 3 at home and tried them. Same thing with all three of them. The spline matches up but the prop won't go all the way on. I tried doing my due diligence and researching the issue, but no luck. What am I missing here?