Stray Current Corrosion?

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I used a reference cell to find a very similar issue. My shaft zincs were going at an alarming rate.
My culprit was a battery maintainer I was trying out for the start bank.
Point is, the disconnecting of anything a.c. powered and watching for change in the reference cell is a great place to start.
That you found the culprit is great, but did you find how this maintainer affected your shaft zincs. DC is #1 source, so how did DC leak into the bonding system?
 
That you found the culprit is great, but did you find how this maintainer affected your shaft zincs. DC is #1 source, so how did DC leak into the bonding system?
I didn’t investigate further. It wasn’t a marine rated maintainer and it had some fancy high frequency routine to keep fla batteries from sulphating. I replaced it with a marine rated one and problem solved. I can only speculate that the ac ground or neutral and dc negative were connected internally.
That connection and the high freq, was a bad deal.
 
Right but I think he means in this case it was an AC powered battery charger.

In this case it sounds like the vessel is on a mooring, so nothing AC unless it's running on the inverter, but certainly not a battery charger.
Yes, I meant an ac charger.
I knew he was on a mooring, and presumably has a genset for ac chargers and an inverter, maybe solar too. No telling what people on moorings do to keep things charged or powered.
It was only a suggestion and an easy thing to check.
 
I watched a rather long NIgel Calder video in search of stray current and why the shaft zinc was wearing out prematurely. Inconclusive in the end but the theory became that graphite stuffing in contact with the shaft and thus the shaft zinc created the wearing. The alternator was also suspect. Again not proved. He was using that silver/silver thing to do the readings.
 
You are anchored 1/4 mile from the nearest boat. Can you move your boat to a different spot for a while to see if anything changes? About 30 years ago I heard a story about a marina owner that wanted a boat to leave that was anchored for months near his marina. He went out one night with several old batteries and dumped them in the water near his boat.
 
You are anchored 1/4 mile from the nearest boat. Can you move your boat to a different spot for a while to see if anything changes? About 30 years ago I heard a story about a marina owner that wanted a boat to leave that was anchored for months near his marina. He went out one night with several old batteries and dumped them in the water near his boat.
That just seems like littering the bottom.
A battery will discharge almost immediately in salt water and have no effect on a nearby vessel unless maybe you dump it on the anchor chain.
 
Start here? This from your post #15: Again I am hesitant to get too granular pondering the numerous little gremlins on a boat, but in the last year I did have problems with several electric tooth brushes charged on both 12v & 120v. Never had a problem with them for several years previously. Finally gave up buying new ones. No obvious problems with other devices plugged in to outlets.

Sounds like something has changed if you are unable to make use of something that worked fine previously. Maybe a combination of an electrical device failing and inconsistent zinc wastage due to other wiring problems that cause inconsistent effects.

Possibly this? This from your first post: I put new zincs on my trawler shafts and in couple months 1 is 1/3rd dissolved (my zincs used to last a really long time), and its active enough that it is the one place underwater that has no growth. I even saw very faint bubbling from that zinc. Other zinc is fine.

Seems like you need to have a look at the drive train on that side. Try disconnecting the engine from the batteries entirely including the alternator if it runs to the batteries separately to see if the fizzing stops. Don't rule out the engine harness to the instruments and controls. If the fizzing stops figure out where the leakage is coming from. Alternators have been known to do that. If it stops, you may be able to begin reconnecting but checking for voltage between the engine and the connection. A voltage or sparking would be clues when you make/break connections.

Make sure you are not using the engine as a DC negative buss bar. Better to move those connections to a separate buss bar with a direct path back to the negative buss.
 
You are anchored 1/4 mile from the nearest boat. Can you move your boat to a different spot for a while to see if anything changes? About 30 years ago I heard a story about a marina owner that wanted a boat to leave that was anchored for months near his marina. He went out one night with several old batteries and dumped them in the water near his boat.
With very rare exceptions, location should have no effect unless the vessel is connected to shore power, and thence to shore ground and other vessels ground/bond systems. Being moored adjacent to a steel bulkhead, for instance, and being plugged into shore power, can lead to a case of the vessels anodes protecting the bulkhead. Of course this assumes the vessel has no galvanic isolator or isolation transformer. Batteries in the water have no reference to the vessel and would have no effect.
 
Thanks for all the responses, I didn't know this thread was still going. I got sidetracked with other things. And now this is back to #1 priority.

Can someone explain this for me:
when using the reference annode, if i connect to the engines or the staring battery I'm not seeing movement on the multimeter when flipping switches. However if i connect to the house shunt at the lug that only connects to the negative cable that goes to the house batteries, then i get mv fluctuations for flipping basically any dc house load on. So then i went and connected to the other end of that negative cable right where it connects to the house bank -- and i get no mv movement on the meter.

Can anyone explain this?
 
I watched a rather long NIgel Calder video in search of stray current and why the shaft zinc was wearing out prematurely. Inconclusive in the end but the theory became that graphite stuffing in contact with the shaft and thus the shaft zinc created the wearing. The alternator was also suspect. Again not proved. He was using that silver/silver thing to do the readings.
I watched that too, and I also have graphite packing, however i have had it for half a decade. Also was it hypothesized that it's only a problem when the shafts were spinning, or is it even a problem at rest? Because my shafts havent been spinning much, and certainly not when my anchor was deployed.
 
I did not see a final conclusion, just a theory.
It is supposition at this point, I guess that is why it is called stray current.
 
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