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Replace Zinc Anode and Test Hull Potential - Oct 2016

posted 14 Oct 2016, 02:47 by Geoff Head   [ updated 10 Dec 2017, 01:59 by Geoff Head ]
13 Oct 2016 - Contracted Underwater Services to check/replace shaft anode. Their report was:  "We have changed the anode on Halo. There was still life in the old anode but it was loose on the shaft and it couldn't be tightened."

I then measured the Hull Potential from the prop shaft (inside the engine room) using the new silver reference electrode.

Measured -970 mV which is within the recommended range according to :  Fiberglass w/ Inboard Engine(s):   -750 to -1000 mV

Update April 2017 - Measured  -870 mV

The same test from the Engine Block gave reading of -340 mV.  According to Bob Olsen of

"Since your engine is not attached to a bonding system that connects to underwater metals, and since your engine is not submersed in water, you do not need to be concerned with the reading from the engine block".