Meesh, Magnum 91 FSR weighs 3 oz. more than an OS 61 and I believe it has more thrust. I'd like to swing a bigger prop, but the arc would reach the spray. The 13" just stay free of it but occasionally I can hear it as it it getting up on plane. The balance as I described it is right on the money and the performance is satisfying for me and will keep up with my flying skills.