I have a 1991 60hp 3cyl Johnson it has an aluminun 13 1/4 x 17 prop on it. With a load it will turn 5900rpm trimmed out it turns 6200 I have a chance to buy a OMC Raker part # 394758 prop but I am not sure it will fit it is a 13 1/2 x 18 it said it will fit OMC Cobra but I am not sure what the Cobra means.