CAPAC and Hull Potential question

[barkleydave]

AC leakage while extremely dangerous will not effect your galvanic readings. You must check for stray current when voltmeter etc. Your .1 reading may be due to loss of continuity between anodes and your hull. (Adding the external mag. anode will tell you real quick.

http://www.boatzincs.com/hanging_anode_magnesium.html

dave

[Tranquilo]

Yeah, thats why I'm alarmed by this. I'm not connected to shore power and am far up river in mostly fresh water.

I'll kill the breaker to his boat and check again today.

So my nodes don't have to be eaten to have that reading? It may just be the current?

I have a ton of extra nodes laying around. Does it need to be Magnesium?

[ericinga]

The magnesium anode will corrode faster than the typical aluminum (Sealloy) anodes. You should use the aluminum anodes especially if there is a potential for brackish water.

That said, hanging aluminum anodes over the side will help protect the hull. As Dave said, the magnesium anode would corrode faster and give a quicker indication of a galvanic problem.

[Tranquilo]

Awesome. Just ordered it

[jralbert]

I know this may be stating the obvious but just to make sure: when you hang whatever you use over the side, it has to be connected to the hull. Stainless wire clamped/tied to a cleat or stanchion or rail. Hope it solves your issue.

[Rob]

Thanks I was wondering if you had to clamp it to the hull, how deep and best spot for it?

[barkleydave]

Stantion or cleat works fine Best location forward of the rudders about 1ft below waterfline

[Rob]

Great, Thanks

[Tranquilo]

Should get it today.

I took the boat out and tested it on a beach. Still read the same but inspected the nodes and bottom. Looks the same as last time I saw it.

I'm leaving for Cuba tomorrow so I'll dangle it over and continue the search when I get back next week.

Can I make extras and dangle lead diving weights as extra protection? I have a bunch of stainless cable laying around so I could make a few of those as well if it would help..

[jralbert]

No on the lead. It's got to be appropriate metal on the galvanic scale. Without that scale in front of me I can't recall where lead fits. But it could do more harm and absolutely no good(have a good trip)