I think the 13X4 would work fine. The 13X4W may be better for your 4 stroke. I am guessing anything in the 14 inch would be a bit much for a Mag 61. I suspect the weight will not be an issue for you. Although I do not know the weight of the 61, it probably isn't much more than a 2 stroke. In addition, you'll probably need the weight of the 61 to help balance.