Stray Voltage/Current at Marina

I really appreciated your newsletter on stray voltage. I am dealing with this very problem and throwing the last two years of my life into research as to how to avoid it at marinas. I have stockpiled enough equipment to test anything. I can offer solutions to some marina tenants, but the waters will always be hot in my opinion.

Two years ago, my company was asked to handle an insurance claim at a local marina. A wire had come loose during a tide change and lay just feet from a sailboat. The boat had a steel keel and no protection. The owner asked what I thought. I told him that the sailboat should have come with protection from the factory, especially since it was a $250,000 vessel. I then called the manufacturer. They claimed that protection units were too costly and so did not install them on their vessels - even the $250,000 ones! The marina owner paid the claim for the damage to the customer's yacht and then the customer approached me, asking for help. He wanted a protection unit. I told him they were around $1,000 but that seemed too much money for him. Then, he requested a galvanic isolator. That unit is only around $100 and offers protection to a meager 1.4 volts.

Shortly after that, the local divers called me and stated that the zincs were foaming off of some of the boats at that same marina like Alka-Seltzer tablets. I immediately dropped what I was doing and went to investigate. There were 32 amps on the marina ground lead. I called the owner of the marina and he simply could not believe me. I was a new technician in town that was making waves.

He called the contractor that had performed a large amount of work at the marina the year before. The contractor had been in business for over 30 years and had a rather large operation with several employees and quite a fleet. When he arrived at the marina, the owner immediately voiced his complaints against me. The electrician asked his employee to test the ground lead at the end of the marina. When the employee opened the power box at the marina's end, the ground was unhooked. Wanting to attach the ground lead to the respective terminal so that the Fluke clamp-meter could be used, when the wire touched the terminal post, sparks flew from the wire, scaring the employee, marina owner, and electrician. The electrician insisted that his employee attach the wire with sparks flying and then clamp it with the Fluke. There were 32 amps on the ground lead. The electrician was horrified to say the least. I do not know if anyone reading this knows what 32 amps on the ground lead at a saltwater marina means, but I know that every professional reading this only has to think for a split second to come up with several scenarios.

The marina owner agreed to have a substantial sum of money spent on the marina's electrical wiring. But still, no one really got the point. While everyone was still present, I unplugged one boat and the amperage on ground dropped by 12 amps! The boat owners were present on the vessel. They claimed that their friend made their shore cord. I traced every boat causing the problem and serviced the wiring. One tenant had the hot and ground reversed on his space heaters.

I was asked to test another marina with over 500 slips and give my analysis of the marina. What I found was astounding. Forty percent of the vessels tested were miswired. The test was bogus as many of the tenants were not present and things can change with the power turned off or unplugged. So, the number could have been even bigger.

I own a magnetic field strength tester, which is very handy in testing if appliances such as water heaters or battery chargers are working before climbing down into the bilge to look. I took it to a large metal culvert that was between the marina and a substation only six blocks away. My meter was off the scale. The culvert is in the bay water and in the soil. I knew where the lost energy was going - back to the substation! Millions of dollars worth a year, costing boat owners millions more in premature zinc loss, pitted and damaged prop shafts, props, trim tabs, thru hull fittings and paint. Just to name a few items I have seen. Rudderposts are another.

If anyone needs help, please feel free to contact me or visit our Website at

Dave Garner
Garner Services
1(360) 956-1190

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