No, I do not think you would feel it until it actaully seperated. You have a lot of distance between the prop and the hull. Every time you go through a gear you dampen the vibration significantly. That is why I mentioned to check everything else in the line shaft etc. There has to be wear on other components, even though not readily visible.
Picture the relationship of taking a coat hanger and bending it until it heats and breaks. This is what Strip's prop may have experienced. That is why there is a crack in the other blade as well. Once one went there is a significant prop imbalance situation.
I have also experienced props getting out of balance just through running. Not NORMAL running but high HP boats producing excessive load through a lot of torque. Slamming the throttles out of hole may actaully bend a prop blade or blades enough to cause this problem. So it could be the way the boat is operated. It only takes once and the damage may be slow wearing and not show up for hours.
[SIZE=3]I had to have my drives rebuilt last year. The prop shaft splines were twisted like candy canes. HP + a little flying + high RPM's on re-entry = bent or broken stuff.[/SIZE]