ABYC E-2 bonding for thru-hulls

ABYC E-2 requires all underwater metal fittings on boats with a bonded electrical system to be connected to the bonding conductor. This includes bronze thru-hulls, seacocks, propeller shafts, rudder posts, and stern gear. The purpose is to keep all underwater metals at the same potential so galvanic action is directed at sacrificial anodes rather than at the fittings themselves. Exceptions: an isolated metal fitting (electrically insulated from all other metals) may be left unbonded, this is common on wooden boats or when a specific fitting is deliberately isolated to prevent stray-current damage. Bonding wire minimum size: 8 AWG for main bonding, 10 AWG for tap connections. Use green or green-with-yellow-tracer wire. Connections must be tinned copper, sealed against saltwater, and inspected annually. A properly bonded system will consume its anodes in 1-2 seasons, anodes lasting longer than 3 years suggest a broken bond, anodes gone in weeks suggest stray current from a nearby boat or shore power fault.