That smoke isn't magic

I am 'refreshing' a pontoon boat. I want to put in a small breaker panel as the power supply to the console electronics. Nothing major. A basic stereo (2 speakers), the running lights, horn, single cigarette lighter.

What guage/size wire should I run from the battery to the fuse panel? My research suggested a 4AWG wire. I need to go about 12 feet of distance from battery to the fuse panel.

Wiring the stereo in and cleaning up the driver console is easy once I get the panel in. I am just not sure of the guage/size wire to carry enough power from battery to fuse panel.

I know, a pontoon is not 'autoelectrical'. I am just trying to get a little guidance/assistance on this project.