It's a delicate balance of measurments, getting the engine positioned for the correct CG, then installing the drivetrain with service area while trying to maintain minimal shaft angle. Distance between the prop hub & strutt should be kept a a minimum with just enough room for a puller to get in there. Usually about 3/4" Next is the prop itself the older boats were designed around the Michigan Wheel props that had short raked blades, the newer props increased the rake like an OJ which creates more cavitaion on the rudder.
