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After my boat was hauled yesterday I noted that the prop zinc as well as the shaft zincs looked brand new. In prior years I would go through almost two a summer. What's different this year?
1. Installed two new house batteries (pair of six volt Rolls), could have screwed something up or perhaps fixed a prior problem.
2. Installed a BlueSea battery link between the house and starter battery
3. Installed a Balmar SmartGauge
When the boat is on the mooring I do drop a large sacrificial zinc off the side and connect it to the pushpit railing. Everything has appeared to be normal during the summer.
Should I be worried by no longer having my zinc loss? What should I check?
Yes, all zincs should show some wear. Perhaps your drop zinc took most of the hit, but it's hard to think both the shaft and prop would show none. Were they well grounded onto clean metal?
Can't count on a dropo're the side zince doing any good unless the shaft is connected (electerly)to the railing and railing to the zinc. THis usually means a shaft brush and other thoughtfull stuff.
Is it possible the zincs weren't properly bedded to the prop? Maybe there had been some build up or they weren't clamped down completely? I think I've also read somewhere that overzinc'ing can cause a problem and results in not providing any cathodic protection. Just some random thoughts.
I thought, the larger the cathode, relative to the anode, the faster the galvanic reaction, but not that there could be no reaction the other way around.
The prop and shaft zincs were put on properly. Sanded surfaces to which they were attached and firmly attached. As usual, hammered the shaft zincs and retightened to ensure good contact.
It could be (my most optimistic thought) that in replacing the house batteries I correct some issue that caused the prior rapid loss of zincs. My zincs aren't absolutely pristine but show very little wear.
Is there some continuity check I should make with the shaft and the grounds?
Showing "very little wear" is fine. The initial description was "brand new".
On the face of it, I can't say galvanic corrosion would have been impacted by your upgrades, but something you changed in the wiring might have. You didn't happen to change marinas along the way or change your practice of being plugged in?
Same zincs, same mooring, same practices. But I'm going with the optimistic assumption that I "fixed" something in the installation of batteries and SmartGauge that previously caused the high rate of zinc deterioration previously. Always the optimist.
Might I tell you about a zinc I once had. Mounted on both sides of a steel plate rudder , well grounded ,,in the prop wash,, lasted for many years .Other zinc (3x5") under the cutlass, bonded with a shaft brush was replaced every year.. The rudder zincs were still as new when I finally sold the boat so I figure they were made in China of quality material.
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