prop size

[RidgeRunner]

Sounds like the 17 is too much prop. If you overprop you loose speed and kill the motor as Destroyer said. I think the 165 was made to tach out at 4600 wot. I would try a 15 and see what happens.

[Blue_Runner]

What they said..........

Unfortunately for you going down to a 15 pitch prop is going to detract from your top end. How is the hole shot? Does she come up pretty quick or a little sluggish when loaded?

[spareparts]

15 may help with top end as well, it allows your motor to reach an rpm where it makes more power than at 3800, look for a big ear 15(flat blades), they used to work pretty good with the straight 6 motors