You need to borrow or buy a clamp-on ammeter (and ideally, borrow the owner to show you how to use it or to use it for you) and measure the current when the pump is running. Then compare that current to the current for that horsepower motor.
I suspect that you will find that it is drawing more than the correct current.
Causes of drawing too much current are usually one of the following:
1. There is a hole or split in the pipe from will to tank that is bypassing a large flow, which overloads the pump, OR
2. The impellers or motor have been damaged or there is other damage that is causing the pump or rotor to drag, causing it to draw too much current.
In rare cases you could have a power leakage due to bad insulation. That is usually not the case because such a failure will usually draw enough current to trip the circuit breaker.
Another possibility is if you have a Pump-Tec or similar device that shuts the pump off on low water, and often has a time delay to let it restart.