I was out on the lake today and every thing was good until i got unusually high rpm's and no power lost all speed and had to limp/idle back to dock i am thinking spun prop and am trying to order new one but is it a Yamaha prop or merc its a 1984-87 15hp Mariner 2-stroke tag reads 15m 684C S 040758 prop is white in color and one of the blades is stamped 9.25x10.50-J