Marine wiring must handle saltwater corrosion, constant vibration, and moisture. ABYC (American Boat and Yacht Council) standards specify tinned copper wire for all marine applications. Untinned copper corrodes rapidly in a marine environment.
ABYC E-11 requires tinned copper conductors with marine-grade insulation rated for at least 105°C. Standard household wire (NM-B, THHN) is NOT acceptable for marine use. Use SAE J1127 or UL 1426 (BC-5W2) rated marine wire. All connections must use tinned or marine-grade terminals.
Most boats use 12V DC systems. At 12V, current draw is 10x higher than 120V for the same wattage. ABYC allows a maximum 3% voltage drop for critical circuits (navigation lights, bilge pumps) and 10% for non-critical loads. Use the ABYC conductor sizing tables, not NEC tables.
Navigation lights: 14-16 AWG. Cabin lights: 14-16 AWG. VHF radio: 12 AWG. Bilge pump: 12-10 AWG. Windlass: 4-2 AWG. Bow thruster: 2-2/0 AWG. Shore power cable: 10-6 AWG (depending on amperage).
Use only tinned copper wire and marine-grade heat-shrink connectors. Apply dielectric grease to all connections. Avoid mixing metals (galvanic corrosion). Run wires above the waterline when possible. Use cable ties rated for UV and marine environments.
Disclaimer: This guide is for informational purposes only. Always consult a licensed electrician and follow local building codes for actual installations. Wire sizing depends on specific conditions including ambient temperature, conduit fill, and derating factors.