Arduino Motor Shield Question

Hey,


I'm looking to build an RC boat using an arduino uno and a motor shield. My motor shield power source is an 18v dewalt drill battery. I want to use this motor : http://www.hobbyking.com/hobbyking/store/__8595__2040SL_4800kv_Brushless_Inrunner_WaterCooled_.html
but the max voltage is 11. How can I compensate for that? Could I just turn down the PWM? a resistor maybe? Thanks for the help,


-Ian
 


Put a voltage regulator between the battery and the shield.