[Zerex]

I took the boat out today fishing and I had the alarm buzzer sound on the controls 6 or so times. It's still pees water fine but I noticed when the alarm is sounding the pee water is luke warm as compared to ocean cold any other time. It seemed to do it after i would run wide open and then slow down to idle. So I would shut the motor off for a couple minutes and then refire it and all would be well and the water temp was back to ice cold.
Does this sound like bad impeller, blockage or faulty thermostat?
ANy help would be appreciated before i have to take it to be serviced

[Zerex]

ANy ideas? Does it sound like impeller even though it still pees strong. I've read about a poppet valve also causing overheating. DDDoes anyone know if this engine has 1?