Alarm sounds 454XL

[bluejamesman]

We took 21 year old Happy Ours out for a 2 hour run on Saturday, 6-28-14 and it ran beautifullywith 1660 hours.
Monday evening, 6-30-14 while checking the boat on the lift behind our home I heard a horn blowing.
It was the VDO starboard horn down and to the right of the steering wheel.
Last night the only way I could get the horn stopped was to disconnect the battery with the switch.
Tuesday AM I checked with power, still a horn.
I decided to disconnect one of the wires to the VDO and repower and the horn stopped.
Then decided to run and freshwater flush both engines , Port engine no problem
Starboard engine, no problem until turning the ignition key "OFF" and the engine continued to run.
The only way I could get it to stop was to kill the battery with the switch.
I heard several different horns when I was trying to analyze the problem but I can't determine which horn is associated with which function. Could It be a sender or ignition switch?

 

[bluejamesman]

Well, it is not the ignition switch, I changed it out with a new switch and powered it up and the horn started blowing, same as before, I need help.

 

[jtybt15]

You didn't give an answer to my response and now it's a horn?

Horn or alarm???????

...and you have two questions about the same problem. How about getting rid of one.

 

[bluejamesman]

Sorry for the confusion-- I have referred to horn or alarm being one and the same.

 

[Sandy]

Check the on-engine alarm switches ( not gauge senders) for oil pressure, coolant temp and transmission temp if I/B. See if they have continuity to ground when they shouldn't.
Look for errant wires to them touching the block , and barring that, look for chafed/grounding wires between the alarm and engine switches, and possibly even wet harness connectors.

If the alarm is sounding with battery switch on but ignition switch off, it is likely wired incorrectly to provide power that bypasses the new ign. switch internals.
Does the engine still keep running with key just turned to full OFF, as you indicated had happened before replacing that switch?

Do you have a high-water bilge alarm?

 

[bluejamesman]

Horn sounding problem solved. The main power connectors located in the helm console were taken apart and some corrosion was present. Cleaned the connectors with CRC and treated with Dielectric. Re-assembled and powered up and no sound was heard. Cranked engines successfully.