Re: OMC side control beep alarm
Hi Turbo,
Chased that exact problem earlier this year. The steady tone is supposed to be for overheat....since your motor is cold we know that isn't the case.
Either the horn itself or one of the pick-up sensors has likely gone flaky on you. In my case, it was the low oil sensor in the oil tank. The other possibility is the temp sensors on the cylinders.
To test the oil tank sensor, follow the wire from the oil tank into the engine compartment. At some point you'll come to a connector that is likely covered by a rubber sleeve. Peel/roll back the sleeve and detach the connector. If when you turn the key on the horn doesn't stay on, you've found the problem. You can either replace the sensor or just leave it disconnected and make sure you check your oil level regularly.
If the horn still sounds, reconnect the oil sensor line and follow the same "disconnect" procedure with the temp sensor(s) (tan wire coming out of the cylinder head).
If the horn is still sounding after disconnecting each of the sensors, I'd say your horn has bit the dust. Those are a little expensive (around $70 I think) at the dealer but they occasionally come up for $10-$20 on ebay.
Good luck!