What is a bonding system?
ABYC recommends bonding all metal parts, which come in contact with seawater. Using #8
gauge green, or green with yellow stripe stranded wire, each part is connected to a common
bus that leads to the motor. This is called grounding. The purpose is to neutralize all the
metal so if any electrical charge is built up, it will be harmlessly grounded back to the negative
terminal of the battery. This includes any type of electrical charge at the fuel fill. But just as
important, think of a bad bilge pump float switch that is leaking 12 volts of DC current into the
seawater in the bilge. All that electricity is dieing to get back to the battery negative, so it finds
a brass through-hull sea cock and flows out into the salt water to the propeller shaft back up
into the boat to the negative battery terminal. That through-hull will become an anode and
eaten alive in just a few hours. The boat sinks! The bonding system would have been an
easier pathway back to the battery and avoided damage to the through-hull. Note: Bonding is
not meant to protect from lightning.
ABYC recommends bonding all metal parts, which come in contact with seawater. Using #8
gauge green, or green with yellow stripe stranded wire, each part is connected to a common
bus that leads to the motor. This is called grounding. The purpose is to neutralize all the
metal so if any electrical charge is built up, it will be harmlessly grounded back to the negative
terminal of the battery. This includes any type of electrical charge at the fuel fill. But just as
important, think of a bad bilge pump float switch that is leaking 12 volts of DC current into the
seawater in the bilge. All that electricity is dieing to get back to the battery negative, so it finds
a brass through-hull sea cock and flows out into the salt water to the propeller shaft back up
into the boat to the negative battery terminal. That through-hull will become an anode and
eaten alive in just a few hours. The boat sinks! The bonding system would have been an
easier pathway back to the battery and avoided damage to the through-hull. Note: Bonding is
not meant to protect from lightning.
From the Surveyor's Notebook
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