One of the worst offenses we see on boats is the use of extension cords and other non marine wire, even such things as audio speaker wire and household lamp cord on high voltage systems. No, I'm not kidding. speaker wire carrying 125 volts. You should never use household wiring devices, such as multiple outlet expanders, or wire. Purchase electrical supplies only from a reputable marine supplier. Wire must have the proper temperature, water and oil resistant ratings and is hard to come by at retail outlets.