I really hate to say this ........... but I agree with fishn_a_ledge on this one "LOL" I have a small 40hp Mercury and the SS was about 3x more and as stated I could buy 3 aluminum. I have nicked (destroyed) one by backing into a rock (back into is never good) but did not hurt the lower unit. I have 1000hrs on motor and have hit a lot of stumps, etc. without much damage to the prop. But it has always happened a low rpms.