I got my boatzinc reference probe and did some testing. Testing was done at anchor
with the probe hung over the side near the prop. Here’s the results….
Test conditions. “Fish” zinc on shroud
and 1 shaft zinc
______________Bat sw OFF _____ lots ON _____ Eng@1100rpm
Shaft__________ -957mV__________ -965mV_______ -935mV
Engine_________ -850mV_________ -885mV________ -903mV
Bond Wire @ bat -855mV__________ -878mV________ -900mV
Keel bolt_______ -867mV__________ -858mV________ -850mV
Water____ -579 to -649mV___ -574 to -640mV*_ -581 to -776mV
Bnz Thru (unbond) -146mV________ -146mV_________ -146mV
* Bilge pump
running/not running had no effect on voltage in bilge
Bilge water voltage would start out high (more neg like -660) then reduce over a few min to -580mV… maybe because I’m using el cheepo DMM?
Partial Repeat with fish
zinc out of circuit, only 1 shaft zinc
_________________Bat sw OFF________ lots ON
Shaft______________ -890mV_____________ -875mV
Engine_____________ -657mV_____________ -663mV
Bond Wire @ bat_____ -663mV_____________ -670mV
Keel bolt____________ -658mV_____________ -675mV
Bilge Water_________ -385 to -420mV______ -402 to -470mV
Bnz Thru (unbond)____ -145mV____________ -144mV
I would love people to weigh in on some conclusions. I’ve drawn my own, and have some questions, but I don’t want to influence you, so….
The bonding wire was connected for all tests. Runs from the negative side of battery
, to engine, engine to keel bolt, keel to mast
. I have lost
quite a bit of lead in my keel.. a few pounds probably over the last 2 seasons.
Thanks for your comments/suggestions.