Thanks mgnostic; I looked at the info on the Balsa USA Sopwith and it said " Four stroke--40 - 50" so I was hoping my Saito 45 Special would be enough, but I do have a Tower Hobbies .46 2 stroke I might think about putting that on it. It is supposed to be .1 HP more than the OS Max .46 FX ! Thanks again. George.