Friend..use a simple circuit, with LM ic, so you can wire it as a comparator,so it can control the voltage to the motor independently...for more presice you can also use a RPM sensor, made out of infra red led, and a opto coupler...so it will determine the speed of the motor while running...and if you are not willing to go this , you can simply alter your speed by using an additional servo...i will post a detailed posting by tomorrow...today i am not feeling well...cold...hi...hi...i will post some simple circuits about, independent motor control with two servos, with micro switches, with three servos with speed controller, with three servos with three motors one for bow thruster...all in with a finger touch...