I fished with a guy yesterday whose buzzer started going off as soon as he fired the motor. He shut it down and started it 5 or 6 times and then it quit making the noise.

He recently changed the impellor, seems to have a strong stream, but doesn't have a pressure gauge. Since his buzzer quit after a few starts and didn't not go off again the rest of the day, what do you think (stuck thermostat or something else)?