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Electrolysis question

Jan 24, 2017
Hunter 34 Toms River Nj
Just looked at a friends boat this weekend that was in salt water for one season, Apirl - October.
He relocated his boat from the entrance of the maria into a more protected slip into the inner lagoon. His new location obviously has a major electrolysis issue. All the zincs on shaft, strut, keel were completely gone. Minor Pitting on the prop and strut due to the zincs being completely eaten away. Note nothing changed other then location, and never had an issue before.

Checked all dc grounds on boats bonding system, negivtive on batteries, dc panel, bildge pump connection, and so on, everything appears good. I don't think the issue is coming from his boat, I believe that the issue is stry current near the boat that could be another nearby boat or possible stry current from the marina.

We have contacted the marina manager to look into this issue, however have not received any response

My suggestion is to add more zinc anodes plus two hanging zincs fore and aft that are bonded to the grounding system of the boat.

My second suggestion is to haul the boat mid season, inspect and replace the zincs if needed.

His thoughts are add more zincs and attach a battery jumper cable to the bonding system of the boat and attach the opposite end of the cable to a grounding rod driven into the ground in the parking lot. I think this is a bad idea. I'm not an electrician so I can justify my reason other then a Gut feeling.

Any feed back or realistic solution that I can pass on to him would be greatly appreciated.

May 17, 2004
Beneteau Oceanis 37 LE Havre de Grace
(I’m not a professional electrician and would defer to those who are, but...)

Intuitively I don’t think the grounding rod would help. Assuming the boat is wired properly and uses shore power, the bonding system is already connected to ground through the shore power cord, so an extra wire to the same place wouldn’t make a difference. The hanging zincs might be the best way to get some extra coverage while the root cause is further investigated.
Jan 11, 2014
Sabre 362 113 Fair Haven, NY
He needs to install a Galvanic Isolator. This will prevent stray DC current from moving through the ground wire on the AC system.

Feb 14, 2014
Hunter 430 Waveland, MS
My suggestion is to add more zinc anodes plus two hanging zincs fore and aft that are bonded to the grounding system of the boat.
One drop zinc, as you suggested, should do the trick until the issue is resolved.
HangTuff™ Hanging Zinc Anode
Hang that zinc at the ≈depth of the shaft and prop and nearby them.

I use it on transient stays in a new marina.

I also check my boat with this.
Corrosion Reference Electrode: Corrosion Quiz

Best thing to detect a stray current too.;)
Dec 23, 2016
Catalina 27 Clinton CT
Run two multi meter leads into the water and look for stray current. That dock sounds like it is hot. Hang extra zincs but X2 on the galvanic isolator. It is stray current coming from the AC ground wire
Apr 14, 2009
Sabre 28 NH
Why not just unplug the boat from shore power until the issue gets resolved?


Jan 20, 2005
Nauticat 321 pilothouse 32 Erie PA
boats moored near aluminum hull crafts (like old carvers) in our marina went thru zincs at a much faster rate and had a lot more electrolysis damage.