In early May I was planning to write a post about how we fill our fresh water tanks on LA VITA. Part of the process includes our Spectra Water maker.

I was in the lazarette talking pictures of our Spectra Water maker when I noticed green and white “fuzz” on the thru-hull and seacock. This is the classic sign of electrolysis.

We have a bonded boat, which means each thru-hull and seacock is connected with a grounding wire. For the bonding system to work properly the ground wire must be continuous and each connection point clean and tight.


We immediately did our local research. After we gather our facts, we contacted Jim (Starfish Marine, now in the Seattle, WA area) and asked his advice. Jim installed all of our electronics and we highly respect his opinion. He recommended the first thing we do is measure the voltage at each connection point on each thru-hull and seacock and inspect the bonding wire for cracks in the insulation or cuts in the wire.

We contacted Rick Cummings on s/v CAPE STAR (AKA Mazatlan Marine Services; formerly C & C Marine Services), a local marine repair service, and asked him to correct the wiring problem and measure the voltage coming into the boat. He found 1-1/2 volts coming into the boat from the negative wire in the dock power. After testing power in several vacant slips, he found that our “leg” of the dock had a broken wire. He notified the marina of the situation and they, in turn had an electrician come down and fix the wiring. Before the repair was made, immediately in fact, we changed where we were plugged in, to the slip next door that was not using dock power.

On these docks there are separate “legs” of power. (This particular dock has, I think, three legs.) Boats right next to each other are not usually on the same leg. There appears to be little “rhyme or reason” as to which slips are on which leg. So, plugging into the slip next to us allowed us to be on a different leg where there was not problem. Changing where we plugged in solved the immediate problem but perhaps not the entire problem. We had to inspect and correct any issue there might possibly be with the boat.

In the process, Julio, Cape Star’s electrician, tested, cleaned, and tightened the connection points to the thru-hulls and seacocks. The system is tested again and the voltage reading on our bonding system is now .004; an acceptable level.


This electrolysis problem can lead to serious problems. We heard of one boat where the electrolysis problem was found after it had eaten through the bronze thru-hull and seacock. As a result, the boat started taking on water. The boat was in close proximity to the boat yard. The bilge pumps were barely able to keep up with the leak until the boat could be hauled out and the problem corrected. They were very lucky! They could have lost their boat and worse if the leak had happened at sea.

To view the photo album for this post, click on the camera,

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