Severe electrolytic action

[Portland Billy]

Has anyone heard of ,or experienced, severe electrolytic corrosion caused by action created between boats,
Possibly as a result of the vessels acting as terminals in acidic water ?
The outdrive on my son's cruiser has suffered severe corrosion and total depletion of anodes for no obvious reason.

 

[dpb]

We had bad corrosion on a Bravo 3 drive one year. In five months on a pontoon berth in Poole Harbour the new anodes were gone and the outdrives surface was pitted through the paint work.
Four previous years in the same marina, but not that specific spot, without problems.
Checked the earthing continuity and the mercathode system. Everything ok.
Up till then we always left the boat disconnected from shorepower with the batteries isolated.
This meant that in our case the mercathode was not activated when the boat was left.
We repainted the drive and fitted new anodes. Different berth this year in same area. But this year left shore power connected so that we could leave the batteries on and therefore the mercathode active all the time.
No issues this time with the anodes reducing only slightly.
I am sure there was a location specific issue that one year but what it was I do not know.

 

[Elessar]

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