I assume you are qualified, since you replaced the motor. Since the new motor is smaller than the old one, I wonder if it has a lower duty cycle. Manufacturers fudge HP ratings by reducing the duty cycle. A 1 hp motor with a 25% duty cycle will be smaller and less expensive than a 1 hp 100% duty cycle motor. Poor connections and bad switches can cause low voltage, which in turn, can cause overheating. How old is your switch, do you have a separate timer? Have you repaired the wiring lately. Do you have a good multimeter?