Failed connections can be your system's biggest enemy. Moist air and vibration will kill twisted or wire-nut connections, so make all of your connections with spade connectors. Spray them with CorrosionX or Boeshield T-9 corrosion inhibitor, and then cap them off with heat-shrink protectors. By doing so, you'll extend their effective lifetimes by years. Finally, make sure all wires are loomed and secured every six inches, so they don't swing, sway and chafe when your boat travels through rough seas.