Here's the possible problem (and this might not be your problem) I see and IMO your gearing is fine.... "Sometimes" once a BL motor has been heated up beyond 200 degrees, they loose mass amounts of efficiency meaning they require more power to be pulled to achieve the same results; speed/torque and HP. For the laymen's, ultimately what ends up happening is they heat up quicker. Not to mention, when you temp a motor you get the outside heat, not the internal heat where it's most important.

165 is not something to worry about if your constantly on the throttle for a packs entirety. Unfortunately one can not tell if a BL motor was ran in those temp ranges before one purchases it used.