was going to run wire from battery to fuse block under dash. approx.12' (16ft. ss alum.).not sure of wire size to use. horn,lights,2 fish finders and possibly a radio.
10 gauge is the usual minimum. In your case, that will leave a good amount headroom for any future accessories except high-powered stereo equipment. Be sure to put a fuse or circuit breaker no more than a foot from the battery on the positive feed. A 25 or 30 amp will do it.