Pump motor replacement has hot casing

2016 Memorial Day.

Turned on the pump and hummmm - no rotation. Loosened the mounting bolts, flipped the switch and it came on. Reassembled.

I let the pump run for two days circulating water to oxidize some nasty squirrel and salamander carcasses.

Charged the filter and vacuumed. Pressure spiked to 40 pisg, so I back rinsed, flushed, wasted, back flushed, flipping the switch many times for each change in operation.

Then the motor stopped coming on. Eventually I gave up. Next day it came on but would run for 10 seconds and trip the main.

After going in the basement to set the breaker about 10 times I ruled the motor dead.

Next day I switched the motor since I had a new Dayton motor in storage. All is good - but.

The Dayton motor diameter is less than the AO Smith I replaced. There is a small space under the motor case.

Dayton motor case is very hot to the touch. Too hot to hold for more than 1 second.

Mechanically & electrically everything is good. AFAICT.

Why is that case so hot?

Looking for troubleshooting options.

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?

Hi Pappy and thanks for responding. I replaced the switch about 5 years ago, and the service replaced two years ago.

I have checked all your points, plus everything in the paper that came with the motor.

I guess I will have my electrician come by for a look see.

I appreciate the input.