we were tubing for hours and all of a sudden as we were getting ready to tube again, there was a loud ringing noise coming from under the dash. l unplugged the wire it was coming from, and the boat still ran great, thought it was the gas,because the wire l unplugged lead to the bottom of the boat, but it was not the gas.
It is a 2001 starcraft
there is no rpm , all it has is the gaas, speedometer, and battery meter.It is also a outboard mercury motor

what kind of boat?
what kind of engine?

continuous tone is overtemp alarm. u lucked out, ordinarily it takes about 25 seconds to completely obliterate an overheating motor.

when it overheats, shut it down immediately. it is not a car, it does not have a fan. continuing to run it with a failed water pump or failed thermostat or blockage at the water intakes or blockage in the water jacket, will make it hotter not cooler. u will have a big expensive anchor in no time.

overheat buzzer? if you were running the boat hard for a while and then shut it off, they tend to oveheat when you restart them. l have this problem with my jet-ski and new boat.

Overheating. It is the alarm. Take it down to 1200 rpm untill the temp goes down. Dont just shut it down, it will get hotter yet and blow the head gasket. And plug the alarm back in! (Unless you want a new motor)

There are two reasons for the alarm to go off. One- it is over heating-two- if it is oil injected, the oil reservoir is low on oil-
If it is the oil that is low, simply add oil to the reservoir- if it is over heating- stop pulling a load and slow down the boat for a while. Never unplug the alarm- it is telling you that the motor is about to suffer very serious damage if you do not correct the problem.!