Zinc disappearing fast - not all locations - guidance?

[boatpoker]

Originally Posted by Cowpoos

OP said there was current leakage from the shore power which is AC.

If the boat is wired to standards. The AC ground is bonded to the DC negative therefore a DC leak can be found in the AC ground.

[boatpoker]

Originally Posted by Ween

Aha, I might know enough now to be dangerous. Thanks to everyone.

Everyone says check bilge pump and any submerged wiring.
Check bonding for all external metal.
Check isolator (not sure how to test but will find out).
Then use half-cell to hunt it down.

Testing a galvanic isolator
https://marinehowto.com/testing-a-galvanic-isolator/

[Ween]

Originally Posted by Ween

Maybe someone can point me in the right direction as I attempt to solve this puzzle? Need some clues...

Bought the boat last Nov, launched late July. Boat just hauled out. I was looking at zincs. In 3 months in the water this season the frigoboat zincs are gone!!!

The big hull zinc is really badly pitted and deteriorated. (all zincs were new)

But the prop-shaft and prop zincs are perfect.

Might this be related to the survey finding below and the boat being plugged into shore power at the slip for the last 3 months? Or bad marina environment?

Survey finding>>Shore power supply: 180 Milliamps were measured in the shore power cord, suggesting a possible onboard electrical leak, re-evaluation with a different reliable shore power supply is recommended, service as required

Where would you start solving this?

thank you for any guidance you can provide.

Update. Replaced all zincs. Launched boat. 3 months in slip with NEVER connecting shore power. Hauled boat. Same result, very eroded zincs.

I must have a DC leak I guess?

[boatpoker]

Originally Posted by Ween

Update. Replaced all zincs. Launched boat. 3 months in slip with NEVER connecting shore power. Hauled boat. Same result, very eroded zincs.

I must have a DC leak I guess?

Sounds like a leak ...You have two choices ...

1. Buy a silver/silver chloride half cell and a decent multi-meter and learn how
to track down the leak.

2. Hire an ABYC Certified Marine Corrosion tech to do it for you.

I'd suggest you buy the equipment and hire the tech then hang over his shoulder to learn about your new tools and how to use them.

Remember, once the anode is gone, the corrosion moves to the next least noble metal.

It is extremely rare for another vessel or shore power to cause these issues. 99.9% of the time the boat with the issue is the source of it's own problem.

Retired ACYC Certified Marine Corrosion tech.

[Ween]

Originally Posted by boatpoker

Sounds like a leak ...You have two choices ...

1. Buy a silver/silver chloride half cell and a decent multi-meter and learn how
to track down the leak.

2. Hire an ABYC Certified Marine Corrosion tech to do it for you.

I'd suggest you buy the equipment and hire the tech then hang over his shoulder to learn about your new tools and how to use them.

Remember, once the anode is gone, the corrosion moves to the next least noble metal.

It is extremely rare for another vessel or shore power to cause these issues. 99.9% of the time the boat with the issue is the source of it's own problem.

Retired ACYC Certified Marine Corrosion tech.

Yes sir. Thank you for confirming. I will follow your advice and do this correctly. Corrosion "freaks me out"