I restored a 1983 Searay Seville 4cyl 120hp completely. I put new gimbal bearing when overhauling bellhousing. Prop is locked in forward, splines line up fine, alignment is exact, shift shaft and all linkage are lined up and inserted into sterndrive, the drive slides on past the o rings on the shaft into the coupler, then it stops 1/4 inch from going together. I know the bearing is seated all the way I have checked it. Could the transom thickness have anything to do with this or the distance of the engine from the transom. I am absolutely stumped please HELP