I was mainly answering Mike but adding to your question also. I am not clear on what is being measured, assumed something to ship's ground.
I have not understood the need to ground an otherwise electrically isolated bronze through hull or seacock though I think at one point it was recommended. Michael Brown Windburn C&C 30-1 Date: Tue, 14 Aug 2018 18:07:44 +0000 From: "Della Barba, Joe" <joe.della.ba...@ssa.gov> I am still not clear on how the voltage is being measured and between what points. I have bronze thru-hulls that are not wired to anything. If I measured between them and the lead keel or the engine with the stainless shaft, I am sure I would read a voltage, they are dissimilar metals in salt water. Absent me wiring up the voltmeter, the thru-hulls have no connection to anything else and would not corrode. If you do have all these thru-hulls wired to ground, as is done on some boats, you now have a battery. You need to be sure there is a zinc involved in there somewhere and it had better have a good connection so that the zinc is the part of the battery corroding. IMHO and also the article referenced in another post, I like to make sure my seacocks and thru-hulls are NOT grounded. This eliminates the issue of poor contact to zincs and prevents the boat wiring from being a path for leakage between boats on one side of you and boats on the other, which is something a zinc will have a hard time saving you from. Joe Coquina
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