Try an OS .91fx on it! I have one on my 4*60 and its the perfect engine! Way more power than you need and it doesn't weigh any more than the other .61's out there. I run a 14x7 3blade M/A and I haven't had any problems with overheating....maybe because you don't have to run it wide open to fly. I'm usally around 1/3 to 1/2 throttle most of the time. Its a GREAT engine! I love mine...