well that all depends if the wiring can support 15 amps, if it does, I don't see why not.

Yeah I just crunched some numbers.

12V * 10 Amps = 120 watts. You might tell me the alternator charges at 14.x volts, but that would still make too close to 144w to be safe.

Horns need 144w, a 15amp fuse at 12v would give you 180watts, plenty....again hoping the wiring will support it. I would doubt it wouldn't. The fuse is there to protect the device, the wire should be able to hold much more current to be safe. Guess a factor of safety of 2 on the wires, they should hold at least 20 amps.

That's all nice talk for "careful".