"Ree-Yees" wrote
I also tried hooking the horn straight up to a battery and it did nothing.

Sounds like the horn is bad. Get a new one. (They're way cheaper than
props.) If the new one is still dodgy, you might want to have a look at your
horn button. As part of my winter maintenance this year, I took all my
switches apart and cleaned the contacts. It's really nice having the horn
blow every time I hit the button. My lights come on without having to pump
the switches now, too.