I recently purchased a 9.9 that came with two props. the one on the motor is a 10 x 5", it has been on there a long time the prop on the edges is a bit rough (must have seen a lot of rocks close up) lol. the 2nd is 9 1/4 x 10" new in the box so I know he never had it on the motor. can anyone help with what I would notice different between the two propellers?