Uh... not exactly. Power (wattage) equals IČR or VČ/R. Halve the voltage and you get 1/4 the power. What is probably happening is that the motor has a starting circuit (which has much less resistance, resulting in higher amps during starting until a centrifugal switch cuts out the start circuit), and the lower voltage can't get the motor up to speed to get it off the starting circuit, so it quickly overheats.