That is really
simple, not thought of nor tried that... will if need again comes along.
When horn's sound acted up, or ceased with electricity still reaching it: I've removed rear surround and sprayed lube on internals as well as to adjust tension screw on diaphragm. Horn sound quality can be adjusted with the screw while surround remains off. Only remember needing to do this a few times in over 50 years. Marine horns are pretty good at maintaining actionable resonance.
Salt air can cause problems. Best to have horn mounted on side of exterior wall with bell pointed down by several degrees... helps keep moisture from getting to working parts.
See horn on bridge in avatar.