This guide discusses the common problems related to a motor that runs very hot. If not corrected, a continually overheated motor will fail. Note that it is normal for a motor to run somewhat hot to the touch but if it's too hot to touch or is dis-coloring the paint, you have a problem that has to be corrected.
Pump in an unventilated enclosure - An operating pump needs air circulating around it to cool. It cannot be enclosed in a closed unventilated container or shed.
Pump overloaded - Impeller is too large for motor. If your recently replaced a motor with a smaller motor and did not reduce the size of the impeller, you may be overloading your motor. The smaller motor is trying to move the same amount of water that the larger motor moved because it is driving the same size impeller. This is a common problem when your replace a Full Rated motor with a Uprated motor They both are labeled as the same HP, but the uprated motor is actually 25-50% smaller than the old Full Rated motor.
Impeller worn and rubbing on diffuser - If your impeller is old and the threads are loose or if it is broken by hard debris, it may be rubbing against the diffuser inside the pump. Pull the motor out and check the impeller. Replace the impeller and possibly the diffuser if required. See our guide on "How To Replace A Pool Pump Impeller" for more information.
Note: a partially clogged circulation system or dirty filter will not cause the motor to run hot unless there is little or no water to cool the motor. When the water flow is reduced due to a clog, the pump is moving less water which converts to less work and less energy expended.