Yes. The instructions call for a 20A with the supplied relay. The stock wiring will push the horn for just long enough for the horn 10A to cook off. Use the relay. Get a wiring connection with a blade fuseblock. Run it from the battery to the relay, and then run the horn wire terminals to the relay (they are plug and play). The horn button won't be live all the time because the button is switched. The connectors from the battery to the relay are not well covered (open to the air) so you'll want to put some silicon or something to protect the connections. If you boost the fuse in the fusebox, you're going to end up frying something.
Great horn... but use the relay.
--edited to add--
And just looked at the label (DOH!)
The label says Nautilus Compact Chromed
