Is yours a Lanier? Also, what prop size are you working with... I've tried (on the ground) everything from a 16x8 to a 18x6w... I like the 6W better, but it won't fit with my 120-cut spinner.. guess I'll have to order a wide cut. The 16x8 spins at over 11K RPM, so I'm afraid its too small. Everything seems to pull in the 15 - 16 pound range.