we had a enforcer i got from a gararge sale for 50 bucks. it was well used i bet from the old german .61 on it it has been around a while. with a 11x6 prop my gps said 95mph keeping it flat and no dive help. since then we got a thundertiger .91 and sofar i am thinking it is not as good but the woodblock was soaked with fuel bad and it came apart in the air. we ordered a new kit the other day and are going to get this big engine setup and a 13x8 this time to load the engine. nice thing is the new engine is not much heavier than the old .61