Beeps!
Yes, the electronic system is set up with a series of beeps, short and long, that can be interepreted as a potential problem to your engine or electrical system.
I'm not real familar with this model, my engine of choice to work on is the Rotax.
I don't know that the trouble shooting section of my rotax shop manuals are applicable to your Mercury, but a steady beep signals engine overheating. If this is applicable to the Mercury and if your running it on land with the water hose, does it still beep? If it does, feel the water being exhausted from the engine. Does it feel like it's really hot (careful not to burn yourself)? Water temperature should not exceed 180 degrees. If the engine is still beeping and the water to you doesn't feel all that hot. Check the temperature sensor. Check the wire that attaches to it, maybe its loose or the sensor isn't getting a good ground from the engine.
Remember, this information is from my Rotax guide on what the beeps mean, so it may not necessarily be applicable to the Mercury.......but I have a feeling the engine temperature sensor overheating signal is....
