You probably don't have to follow them.  Just take a voltage reading to
ground just to make sure they are not energized.  Then take a resistance to
ground.  Then take a resistance to your bounding system which may be the
same thing as ground.  Then just for kicks take a resistance reading to the
shaft.  It should be 0 ohms.

Josh

On Tue, Mar 14, 2017, 3:37 PM Matthew L. Wolford via CnC-List <
[email protected]> wrote:

> Thanks.  There are two wires unconnected to anything in the cabinet near
> the thru-hull.  We did major repair work on this boat about five years ago,
> including replacing all the thru-hulls.  This is the only exposed bronze
> thru-hull, and one or both of the wires may have been disconnected for the
> repair and not reconnected.  I will attempt to follow them to see where
> they lead.  Not this week, however.  Brrrr.
>
> *From:* Josh Muckley via CnC-List <[email protected]>
> *Sent:* Tuesday, March 14, 2017 3:05 PM
> *To:* C&C List <[email protected]>
> *Cc:* Josh Muckley <[email protected]>
> *Subject:* Re: Stus-List Zinc decay
> Next time you're at the boat just look for a coupling isolator and a
> ground wire on the problematic thru-hull.
>
> http://www.randdmarine.com/flexiblesc.asp
>
> https://www.gcsmarine.com/content/drivesavers/drivesavers
>
> Josh
>
> On Mar 14, 2017 2:51 PM, "Matthew L. Wolford via CnC-List" <
> [email protected]> wrote:
>
> Okay.  You’re already beyond my level of expertise.
>
> *From:* Josh Muckley via CnC-List <[email protected]>
> *Sent:* Tuesday, March 14, 2017 2:44 PM
> *To:* C&C List <[email protected]>
> *Cc:* Josh Muckley <[email protected]>
> *Subject:* Re: Stus-List Zinc decay
>
> Do you have a shaft coupling isolator/vibration dampener?  You might be
> experiencing stray current on the thru-hull but the shaft might be
> electrically isolated.
>
> On Mar 14, 2017 2:38 PM, "Matthew L. Wolford via CnC-List" <
> [email protected]> wrote:
>
> Not confident at all.  In fact, I’d be surprised if they were connected.
>
> I am also surprised that whatever was going on near the thru-hull was
> apparently not going on 20 feet or so away near the prop, because the zinc
> back there is intact.  I would think that a stray current would not be so
> localized, but I’m no expert.
>
> *From:* Josh Muckley via CnC-List <[email protected]>
> *Sent:* Tuesday, March 14, 2017 2:27 PM
> *To:* C&C List <[email protected]>
> *Cc:* Josh Muckley <[email protected]>
> *Subject:* Re: Stus-List Zinc decay
>
> Matthew,
> Are you confident in the electrical connection between the through hull
> and the shaft zinc? Zincs don't work unless they are in electrical contact
> with the metal they are protecting.
>
> Josh Muckley
> S/V Sea Hawk
> 1989 C&C 37+
> Solomons, MD
>
> On Mar 14, 2017 2:24 PM, "Matthew L. Wolford via CnC-List" <
> [email protected]> wrote:
>
> I have one for you: my bronze sink thru-hull (for the head, which is
> forward of the mast) was green and partially disintegrated when I pulled
> the boat this year.  The zinc on the shaft to protect the propeller was
> fine.  Thoughts?
>
> Also, I just got my hard copy of the scam letter for USCG documentation
> renewal.  I was almost fooled, and I am aware of the scam.  These guys
> should be arrested for fraud.
>
> *From:* David Knecht via CnC-List <[email protected]>
> *Sent:* Tuesday, March 14, 2017 2:06 PM
> *To:* CnC CnC discussion list <[email protected]>
> *Cc:* David Knecht <[email protected]>
> *Subject:* Re: Stus-List Zinc decay
>
> Last year, I posted the message below about unusual zinc consumption and
> got many insightful responses about possible causes.  I decided to do
> nothing specific and see if it happened again this last season.  I can
> report that the anodes were in good shape when the boat was pulled last
> November- much the same as in previous years.  So I am going with the shore
> power stray current suggestion, as I cruised to some new sites last year
> and spent a few days plugged into shore power in a place I have not been
> before or since.  So if that is correct, Joe Della Barba would be the
> winner.   Maybe we should keep score in the future?  Perhaps have a Stump
> the Chumps episode periodically ala Car Talk?  Dave
>
>
> On Dec 24, 2015, at 11:47 AM, David Knecht via CnC-List <
> [email protected]> wrote:
>
> When my boat was pulled from the water this year I was surprised to find
> that the Max-prop zinc was gone, one of the shaft zincs was gone and the
> other was nearly gone.  I have had this configuration in past years and
> every other year at the end of the season I could barely justify replacing
> them because there was so little metal decay.  I know of nothing I did
> differently this year.  I am on a mooring so rarely plugged into shore
> power.  What would cause a dramatic increase in zinc decay?  Thanks and
> Happy Holidays to all!  Dave
>
> Aries
> 1990 C&C 34+
> New London, CT
>
> <pastedGraphic.tiff>
>
> _______________________________________________
>
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>
> Aries
> 1990 C&C 34+
> New London, CT
>
>
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