This engine will really wake up a 40 size airplane and make it fun to fly. I have been using the OS 61FX but now I wouldn't swap the Tower 75 for two OS61s. Best engine for the price out there. Only thing I would suggest is to JB Weld the muffler to prevent it from vibrating loose. I do this for the OS too because I have lost the rear portion on one and it cost almost as much for the Rear part of the muffler as the whole 75 engine costs.