Zinger 16/6 prop, there are better choices! Mine was in a 120 size also, I'm in the process of changing it out to a dle-20 hoping for a little more zip! I think you have the 90 size, the 15cc engine should do pretty good on that size, around 1 to 1 power to weight for the rcgf 15 on the 90 and 20 on the 120 size. Balance your prop, the blades & hub, to help eliminate vibration.