locate front and a single wire can be removed, also you can splice a 2nd wire on, and replace the diaphragm horn, with Frams. or any loud one you like, what you may like to do to protect its circuit is to add waterproof fuse.
the link above is oil is there a horn there for the OP
Wec hanged our horns, for one that does a better job but not over the decibal's.