Re: [Amel Yacht Owners] Re: autoprop zinc

Andrew & Kate Lamb



Can you give some more details about the silver reference electrode that you sued – this seems like a very useful tool to have?






SM2k 472

Canet en Roussillion, France




From: amelyachtowners@... [mailto:amelyachtowners@...]
Sent: Monday, May 04, 2015 9:20 PM
To: amelyachtowners@...
Subject: [Amel Yacht Owners] Re: autoprop zinc





After Kent had his problem with what appeared to be electrolysis on his propeller shaft, I ordered propeller zincs for my Autoprop.  However, I also wanted a definitive answer to the question, "how much zinc is enough zinc?", so I also ordered a silver reference electrode.  With the reference electrode I was able to determine that one zinc on the rudder was too little (~ -0.500 volts) while two fresh zincs on the rudder was in the ideal ranget (~ -0.900 volts).  I was also able to verify that the bonding system was working equally at all points in the system.  According to the reference electrode manufacturer (and Henri Amel) you can 'overzinc' your boat. Thus I have not put on the Autoprop zinc at this time.


The only other zincs that I am using are on the Spurs rope cutter and on the Onan heat exchanger.  These were in place when I made my measurements.


FYI I also measured with and without the shore power cable connected.  The power cable dropped the value about 100 millivolts (to ~ -0,800), indicating to me that I should keep the shore power cable disconnected when not in use - at least in that marina.


all the best,



SM2K #400 Brava

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