Gotta be honest, I'm getting a bit confused by these comments. Isn't the trigger wire meant to be positive and the relay is grounded separately?
This relay diagram shows what I had in mind. Terminal 87a would run a short distance to pilothouse switch and then up to the horn with 10awg wire. When the switch is closed, it will send power the horn since 87a is hot when the trigger is not powered.
87 would connect to the horn wire beyond the pilothouse switch. It would power the horn when Terminal 86 is powered by the trigger wire, which would lead back with a longer length of 16awg wire to the cockpit switch and then to the fuse block (or to the input terminal 30/51).
The horn is then grounded separately, as is the ground terminal (85) on the relay. So the all the switches are indeed on the positive side of the horn wiring
, which is perhaps what your comments referred to.
I'm pretty confident in my plan at this point, but I'm no marine
electrician so if there is something wrong with my thinking about this or something not ABYC complaint then I definitely would like to know and I appreciate the input!