Too Many Zincs???

[denpooch]

Hello crew. I hope all is well.
At the end of last season I posted a few images of what seems to be some sort of corrosion issue around any thru hull component on my 36 ft. Mariner. Most folks suggested that it may be a 'bonding' issue.
Yesterday as I am preparing for a new season, we checked the bonding and the ohmmeter readings showed that the bonding does seem to be concurrent to the engine block and back to the stern zinc.
I do recall in a fairly recent post that our resident expert 'Viper' suggested that 'over zincing' can cause additional problems. Praytell....
can this be the issue with my boat.
I have the following zincs in place, again she's a 36: bow thruster, 2 zincs per shaft, one 5" zinc on each tab and the 'zinc block' on the stern.
The only difference this past season is that I put 'heavy' gauge zincs on the shaft. The zincs that experienced the most 'pitting' and wear seem to be the pieces on the trim tabs.
My mechanic suggested that he has seen this before and attributed it to conditions with the 'dock' and stray current, etc. He doesn't know if anything is wrong with the boat and is not familiar with 'over zincing'. The marina workers think its a boat issue.
What say you? All feedback is appreciated and thank you.

Air Conditioning Intake.jpg

Rudder.jpg

Engine Intake.jpg

Tabs.jpg

[Viper]

That really does look like what I was talking about. The problem is it's hard to say if you've got too many anodes as it really depends on several conditions. If the hardware is properly bonded, I'd get someone to take readings in the water where she's docked. I wouldn't think you'd have too many anodes based on what you posted but you never know. Could also be something else going on but really seems like an electrical issue which is also the science behind how the anodes work. I suspect all your anodes are zinc?

[denpooch]

I appreciate your response. Yes all zinc anodes.
I plan to remove one of the heavy anodes from each shaft and see if that helps.
Question. I have never ‘re-used’ zincs and have always just purchased new. If there is plenty of material on the piece, is it safe to scrape-sand and re-use? I plan to replace the pitted trim tab zincs.
Thanks again.

[Phrancus]

can you re-use: yes. should you: depends. you need material enough to 'dissolve' in the time the boat is in the water. If you take her out during the season, you can check for remaining material.

If the currents do not flow through your anodes then they won't work like they should. Possible reasons: softer material available for your type of water. Or the zincs are not of the right material mix. Or they are not working due to insulation: paint over the outside or bad bonding to the boat (like mounted on a painted surface or bolts not connecting electrically)

In a perfect situation the anodes would burn off really quickly when too high currents flow. When they don't but you do have those currents, as you notice from trouble in other spots then you have more work to do: the anodes is one, and the origin of the currents is two. Lots to measure on your boat and your dock. Too much through the water when docked is not a good thing for swimmers (voluntary or not) either.

I don't know of a premanent 'leakage flow' monitoring gauge but that would not be a bad idea, nor too difficult to make. It would indicate eletrical connection issues long before end of season when it's too late.

[Viper]

Source of the post....I have never ‘re-used’ zincs and have always just purchased new. If there is plenty of material on the piece, is it safe to scrape-sand and re-use?.....

Ya as long as there is plenty of material to get you through the upcoming season, you can keep using them. Just get a wire brush and brush off the oxide which is likely to be coating them, especially if the boat sits a lot. This coating will reduce their efficiency.

[denpooch]

Thanks to all.