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East Coast Marine Surveying and Thermal Imaging Lothian (Annapolis), Maryland Kenneth Roberts, SAMS® AMS® Principal Marine Surveyor Certified Level III Thermographer Serving Maryland & the US East Coast Cell: 301-922-5394 |
Dock Shock is a term we use to describe a measurable amount of electricity in the water. Stray electricity can enter the water for several reasons. The shore power cord connects electricity from the pedestal on the pier to the vessels inlet supply and then travels to the breaker panel, where it is distributed throughout the vessel to operate various components, radios, microwaves, televisions, etc... any one of these components can fail, but still power, with the result being "Dock Shock".
What Does This Mean?This means any place there is electricity, there is potential for "Dock Shock". Any unused electricity on the vessel has a return path back to the pedestal which is measured on the shore power cord with a True RM Clamp meter. Any reading other than "0" can be a dangerous condition. It only takes 1 to 3 mA to get a tingling sensation. At 10 to 20 mA, you can lose Voluntary Muscle Control. At 18 to 22 mA, Paralysis of Diaphragm and Chest Muscles occurs. Heart Fibrillation occurs at 50 to 65 mA and death can occur in only a few seconds if exposed to anything over 100 mA. Here is a picture of an attempt to repair a failed shore power cord. When measured, the reading I got was over 15 amps, not milliamps, but amps. This would have killed someone had they been in the water near this vessel. But my boat is fine! 
Ok, so your boat doesn't seem to have any problems, how do you know if the boat two slips away isn't depleting YOUR zinc's? That's right, any boat that has a "Dock Shock" issue can affect several boats in nearby slips. We had a customer that stated "I have replaced my Zinc's twice this year and that has never happened before". We went for a walk with our meter, and surely enough, 3 slips away, there was a boat that had an automotive battery charger onboard that wasn't properly grounded. Here is a close up picture of the keel of the wooden boat that became the victim of someone else's "Dock Shock".Please help us keep boating safe by inspecting your vessel in it's home slip. Thank you. Ken Roberts SAMS® AMS®, ABYC member Certified Level III Thermographer |
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