Hi Mike: A good book for you is Nigel Calder's "Boatowner's Mechanical and Electrical Manual". In the book, it says: "All equipment should have an insulated ground that leads back to a central ground bus bar in the main distribution panel, which in turn leads to a common ground point or bus." In other words, don't connect one ground to another, and then to the ground bus. Each piece of equipment must have it's own ground going to the ground bus.
Alan On Mon, Aug 13, 2018 at 4:25 PM, Mike via CnC-List <cnc-list@cnc-list.com> wrote: > Hi Alan > > > > The readings I posted are at anchor in the Thousand Island area. I almost > never plug in during the cruising season. I only use shore power to charge > the batteries during winter layup when the solar and wind are removed, > every 6 to 8 weeks > > > > So today I did more testing. I disconnected the positive cable for the > start battery and I still saw 0.02V at the prop shaft. So I ruled out that > as an issue. I disconnected the battery charger and still saw voltage. > Next I took the wind generator out of the equation and the results were the > same. Next I disconnected the windlass, same results. Next I moved inside > and checked for voltage on the tube for the centre board pendant. Saw 0.25 > V. I removed the positive cable to the house electrical panel. Still saw > voltage. > > > > Am I doing this right. My memory tells me that the way I’m testing might > be creating some kind of battery but my memory might be tricking me. > > > > Could really use some help from any electricians or corrosions specialist > out there. > > > > > > Mike > C&C 37 K/CB Shoal draft > Persuasion > Stormont Yacht Club > > > > *From: *ALAN BERGEN via CnC-List <cnc-list@cnc-list.com> > *Sent: *August 9, 2018 5:23 PM > *To: *C&C <cnc-list@cnc-list.com> > *Cc: *ALAN BERGEN <trya...@alumni.usc.edu> > *Subject: *Re: Stus-List Galvanic corrosion > > > > You can use aluminum anodes in fresh water. That's what I use. They're > cheaper than magnesium. > > > > To test for stray currents, borrow a clamp on ammeter. Then check the AC > line supply for your boat, and for the boats in nearby slips. The ammeter > should read zero amps. Use the lowest scale, as stray currents could be > pretty low. If the reading isn't zero, some of the current is finding a > return path, other than through the AC supply line. > > > Alan Bergen > > 35 Mk III Thirsty > > Rose City YC > > Portland, OR > > > > > > On Thu, Aug 9, 2018 at 6:01 AM, Mike Taylor via CnC-List < > cnc-list@cnc-list.com> wrote: > > Hi Bob > > > > I started the season with 1.5 anodes. I’m in fresh water, Lake Ontario and > St. Lawrence river. I believe I have the correct anodes for fresh water. I > really don’t want to go the galvanic isolator route > > > > Mike > > > On Aug 9, 2018, at 12:04 AM, Robert Boyer via CnC-List < > cnc-list@cnc-list.com> wrote: > > What is the condition of your shaft zincs? > > > > Are you in fresh water or salt water & do you have the correct zincs for > the type of water your boats in? > > > > Sounds like you may need a galvanic isolator... > > > > Bob > > Bob Boyer > > S/V Rainy Days (1983 C&C Landfall 38 - Hull #230) > > Blog: dainyrays.blogspot.com > <https://urldefense.proofpoint.com/v2/url?u=http-3A__dainyrays.blogspot.com&d=DwMFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=9w3G7Cf8YfQnrjmtuNxwDJYr3JMv9f1pAfgAJ9xXYQQ&m=fJAQMdpX2dTSopdOWc3l9uX5S1WMFKlmsA86BrWxBCw&s=Wa3qqugmtpAwXVFKMv4mxeeuUh8qI-Q-QEkwBjxxvQo&e=> > > Email: dainyr...@icloud.com > > Annapolis, MD > > > On Aug 8, 2018, at 8:10 PM, Persuasion37 via CnC-List < > cnc-list@cnc-list.com> wrote: > > > Hey folks > > > > I’m looking for some help. Persuasion is suffering from galvanic > corrosion or stray current corrosion or something. When I connect a multi > meter, ground to engine and positive lead to various place like keel bolt, > mast and through hull I see ~0.5V. Today I changed out the controller on > the wind generator, with the circuit breaker open I saw 2.4V on the battery > leads. Also the prop shaft was tarnished looking as well as the prop when > I hauled out to do the centre board. > > > > Before I call in the calvary can anyone advise me how to tackle this > methodically and what I should look for. > > > > > > Thanks in advance > > Mike > > PERSUASION > > C&C 37 *(k/cb) *shoal draft > > Long Sault > > _______________________________________________ > > Thanks everyone for supporting this list with your contributions. Each > and every one is greatly appreciated. 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