Having a problem with bow mounted fish finder shutting off periodically. Currently, finder is grounded directly to starting battery - power line goes thru dash switch. Thinking of wiring directly to group 27 deep cycle I use for down riggers. This distance from finder to battery will be close to 20 ft. What gauge of wire would be best for this wiring and should I be considering marine tinned wire? Some suggest I check the current ground - not tinned and probably 14/16 gauge - for hot spots. Finder is a Lowrance HDS-7.