I recently put a new gauge panel in, today I went to calibrate a new electronic gas sender. When I turned the key to the right, I would normally get an alarm. I did not replace any of the switches, what is that alarm for? And would screwing up the wiring on one of the gauges cause the alarm not to work?

Thanx

What engine set up do you have?

Yeah I was running out the door when I typed that. 1998 454 MPI

If you mean when you turn it on, you get a continuous alarm, that is the low oil pressure sensor going off, since you don't have any oil pressure when not running.

That is your warning horn system, When you first turn the key on, It should sound the warning horn for about two seconds as a self test and to let you know the warning horn audio system is working correctly.

It sounds like you may have disconnected one of the wires going to the horn, The horn only has two wires going to it, One is purple, And that purple wire normally hooks up to one of the purple wires going to one of the gauges under the dash area because it's usually the one of easiest areas to get to for installation purposes, Also so that you can hear it while under way when needed.

The other wire will be a tan with blue stripe going to the horn.

To test the horn system, All you need to do is ensure you have 12 volts at the purple wire with the key on, Then just ground out the Tan/Blue wire, The horn should sound.

For some basic information about the horn see page 53, It's almost half way down in this link.
http://www.boatfix.com/merc/Install/gas/86419602.pdf

I wonder why I'm not getting any sound, this looks right according to you description: The purple goes to the Speedo and the tan and blue goes to somewhere I can't see, I just see it coming undone with the tan and blue.

What kind of speedo gauge do you have? Normally the speedo does not use the purple wire, It would use the blue wires to turn on the gauge light and the black wire is for grounding for the gauge light only.

The horn is usually a stand alone object that is wire tied up out of the way after you plug in the wires going the horn.

Unhook the horn from the gauge, Ensure you have 12 volts going to the horn with key on and double check you hooked the wires up right.

The tan wire goes back to the engine, If you ground it out somewhere it should sound the horn.