Bonding & Grounding System


    1. provide a low-resistance electrical path inside the hull between otherwise isolated metallic objects, especially those in common contact with sea water
    2. prevent the possibility of electrical potential on exposed metallic enclosures of electrical equipment
    3. provide a low-resistance path for excessively high voltages, such as when the boat is struck by lightning
    4. to minimize radio interference. Boats without permanently installed electrical systems do not need bonding.
Corrosion – Zincs
  • Wiring systems on boats are two-wire systems, with the hot or positive wire carrying power to the lights and appliances, and a separate, insulated wire returning to ground, generally the negative bus bar in the distribution panel, which in turn is connected to the common ground such as the engine block. If the boat is bonded, as described earlier, the bonding strip is not to be used as ground.  (Upgrading the Cruising Sailboat, p. 275)
  • The electrical items on a marine engine almost always use a ground-return circuit. That means the engine, rather than an insulated wire back to the battery, serves as the ground side of the circuit. Because components are electrically connected to the ground circuit by their mounting bolts, you must consider these mounts when you suspect a poor connection. A buildup of rust between mating surfaces can open the circuit as effectively as a disconnected battery cable. And speaking of battery cables, the ground return circuit is typically completed through a cable connecting the engine block to the negative battery terminal.  (Sailboat Electrics Simplified, p. 79)
  • Negative Ground – The negative post of all batteries should be connected to “ground” to hold it at 0 potential – relative to Earth. This is normally accomplished with a cable between the negative battery post and a bolt on the engine block, which connects the battery to earth through the propeller shaft. We refer to the bolt on the engine as the “grounding lug.” Multiple connections to ground should be made to a bus connected to the grounding lug. this is the main grounding bus.  (Sailboat Electrics Simplified, p. 38)
Grounding – Alternating Current (AC)
Grounding – Direct Current (DC)
Grounding – Lightning Protection
    1. Avoid all ground connections so that the atmospheric change won’t seek ground through the boat.
    2. Thoroughly ground the boat so that the lightning will have a quick and easy – maybe even painless – way out….we think the [first] is seriously flawed.
    1. If at all possible remain in the cabin of a closed boat.
    2. No one should be in the water or have any part of their body immersed in the water.
    3. Do not come into contact with any components connected to the lightning protection system of a properly protected vessel. Otherwise your body could act as a conductive bridge between any items connected to the lightning conductive system. For example, you should not be in simultaneous contact with a metal steering wheel and a metal stern pulpit.
Grounding – Radio


Links and Resources


Page Menu

Comment Form

* = Required field. Also, your email address will not be published.