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Old 31-08-2022, 18:27   #1
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Join Date: Mar 2009
Location: Florida Keys
Boat: Robertson and Caine Leopard 40
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Disparate saildrive zinc deterioration

After hauling last week for routine mnx, I noticed the sail drive zincs on our '06 Leopard 40 sail cat had deteriorated at vastly different rates. Both were installed 2 years ago. I had noticed this was occurring while cleaning the bottom every couple months but did not realize extent until I power washed and had a good look. Port was down to ~ 20% and stbd one was down to ~50% (they are 15' apart).

When I noticed the zincs deteriorating at different rates, I started checking my corrosion values on both sail drives, thru hulls and engines with a silver chloride electrode and a decent multimeter. Our reference number was determined to be .865mv and both sides always tested good. I now wonder if I have been doing it right

Boat is in a slip most of the time in Key West. We are underway only about 5 days/month.

I do not think shore power is an issue, as the pedestals are regularly checked and we have a working galvanic isolator aboard. All thru hulls are grounded to engines (starboard ones to stbd engine and vice versa).

On our port side is an older 40' cabin cruiser. On our stbd side is a newer Katy Krogan. The port neighbor has had extension chords running thru the water from our shared pedestal to a house window aircon unit for the entire 2 years since we last splashed.

Is it possible my port side neighbor's extension chords and house window unit aircons are the culprit? If not, I'd be interested in any thoughts as to culprit(s). Thank you.
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Old 31-08-2022, 20:08   #2
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Re: Disparate saildrive zinc deterioration

Quote:
Originally Posted by gbillman View Post
After hauling last week for routine mnx, I noticed the sail drive zincs on our '06 Leopard 40 sail cat had deteriorated at vastly different rates. Both were installed 2 years ago. I had noticed this was occurring while cleaning the bottom every couple months but did not realize extent until I power washed and had a good look. Port was down to ~ 20% and stbd one was down to ~50% (they are 15' apart).

When I noticed the zincs deteriorating at different rates, I started checking my corrosion values on both sail drives, thru hulls and engines with a silver chloride electrode and a decent multimeter. Our reference number was determined to be .865mv and both sides always tested good. I now wonder if I have been doing it right

Boat is in a slip most of the time in Key West. We are underway only about 5 days/month.

I do not think shore power is an issue, as the pedestals are regularly checked and we have a working galvanic isolator aboard. All thru hulls are grounded to engines (starboard ones to stbd engine and vice versa).

On our port side is an older 40' cabin cruiser. On our stbd side is a newer Katy Krogan. The port neighbor has had extension chords running thru the water from our shared pedestal to a house window aircon unit for the entire 2 years since we last splashed.

Is it possible my port side neighbor's extension chords and house window unit aircons are the culprit? If not, I'd be interested in any thoughts as to culprit(s). Thank you.
Well, turn your boat around and see of the problem switches to the other side.
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