Yes there are galvanic current flow monitors. I don't believe they are
specific to metal hulled vessels.
If you really want one I suggest you talk with a marine surveyer and
also with knowledgeable folks at your local (ro maybe distant ) Marine
Store. I think Amole Power have a product. You will also find the
subject covered in marine electronics texts at the library. Arild Jensen
may also be helpful. Fluke ( meter people ) have a data sheet
specifically on measuring stray currents and gal;vanic flow. The
solution involves a specific acombination of metals in the probes to
very accurately determine current flow. The bigger question is, so what?
If it is a problem on your vessel you should get professional advice on
the fix because it is not necessarily straightforward in getting a
solution. You could make it worse.
Have fun.
Watch your welds.
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