[Al Skierkiewicz]

I think you need to look at the fact that you have 14.5" tires. You are traveling 45" for every rotation of the wheel. A rule of thumb here is your design speed should be less than or equal to 10 ft. sec. in a straight line. You must reduce the motor output in order to increase torque to the wheels. You are likely so far down on the motor curves that you are drawing near stall current on the motors. (drills stall out at 129 amps.) With the larger diameter wheels it is very easy to draw too much current from the battery particularly in turns. The pump is shutting down because you have drawn the battery down to a point where the RC stops functioning or the pump can't get enough current to run.