1985 Starfire 150 Buzzer in Helm

[rpetot]

Took the boat out for a run yesterday to shake her down before a fishing trip down to GA next week.
Running a 2 stroke Mariner 150.
All went well, except for on the way back to the dock, a buzzer (somewhere under the steering console) started sounding. I've only had the boat for a year and a half, and this is the first time I've heard this buzzer go off.
This is my first Bass Boat too, so yes, I admit I dont know all the ins and outs.
Anyway, not knowing what the warning was for, we pulled off to the side of the lake and shut her down. Fuel was fine, Battery was fine. After a couple minutes of head scratching, I fired it back up. Ran perfect. Had good waterstream out of the motor so I know it was cooling.
Proceded to head for the ramp.
Lasted about 2 minutes and the buzzer went off again.
It stayed on for the last 3 or 4 minuted of the ride back to the launch.
When we got slowed up near the launch, I put the transmission in neutral, left the motor idling, and the buzzer stopped ringing. I dont recall this happening the first time we stopped, but I might have shut it down still in gear in my haste of trying to figure out what the sound was.
I was thinking it might be a temperature alarm, but why would it matter if you were in gear or not.
Before I speculate too much, can anybody give me an idea of what this alarm buzzer might be for, and what if any action I need to take.
I'm heading south next week and want to feel comfy that all is well.

Thanks in advance

[Skeet'r89]

Your motor was probably over heating. At an idle it would stay cool enough. At higher rpm you are not getting enough water pressure to cool the motor. You probably should change the impeller in the water pump. Also a water stream at an idle is not proof you are getting enough water.
Hopefully you didn't hurt your motor.

[rpetot]

Thanks for the feedback. So why would the buzzer shut off as soon as I put it in neutral? Surely the motor wouldnt cool down that quick.
I was getting a pretty good jet of water out of the motor not just at idle, but at RPM as well.
I'll take the advice about changing the impeller. Its an old rig, so any little thing is going to be good for it. It just got a clean bill of health at the shop a year and a half ago, but that was a year and a half ago.

[Skeet'r89]

Maybe you should post your question in the Mercury motor forum. There are smarter guys over there.