The manuals say to remove the propeller in order to remove the lower unit. I don't understand why you have to do that just for a water impeller replacement. I have re-read the manual and I just don't understand why the prop has to come off. Can any one confirm or deny this. My best estimate of this is that the prop CAN stay on for water impeller replacement. I know someone here can give the straight up on this. Thanks in advance.