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Old 20-09-2020, 12:01   #1
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Zincs over the side

I am wondering if I could get some help with information on zincs. Particularly with zincs hanging overboard which I have seen quite a bit at marinas. Are they a good idea given unknown hazards at a marina? Where ahould a guy connect them to, engine, shaft etc? My shaft zinc seems to go quickly at the marina although with a Beneteau 373 the shaft zinc is quite small.
Any other information would be helpful.
Thanks
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Old 20-09-2020, 12:05   #2
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Re: Zincs over the side

Do you have a fixed-blade propeller?
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Old 20-09-2020, 13:17   #3
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Re: Zincs over the side

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Are they a good idea given unknown hazards at a marina? Where ahould a guy connect them to, engine, shaft etc?
See #20 and #21: https://www.cruisersforum.com/forums...ml#post1112097
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Old 20-09-2020, 15:14   #4
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Re: Zincs over the side

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Do you have a fixed-blade propeller?
Yes, the boat has a fixed blade prop. I am quite curious how that will relate to the zinc question.
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Old 20-09-2020, 15:16   #5
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Re: Zincs over the side

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Yes, the boat has a fixed blade prop. I am quite curious how that will relate to the zinc question.
It relates because every Beneteau with a fixed-blade prop has an anode on that prop. Yet you make no mention of it.
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Old 20-09-2020, 17:39   #6
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Re: Zincs over the side

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It relates because every Beneteau with a fixed-blade prop has an anode on that prop. Yet you make no mention of it.
Yes, I mentioned the shaft zinc twice. Do you know anything about a zincs attached to the engine block?
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Old 20-09-2020, 17:53   #7
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Re: Zincs over the side

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Yes, I mentioned the shaft zinc twice. Do you know anything about a zincs attached to the engine block?
The anode on the prop is not a shaft anode, it is a prop anode. Prop anodes on French boats are notoriously undersized in any case. You need to add a shaft anode.



https://www.boatzincs.com/BD-25.html
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Old 20-09-2020, 17:57   #8
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Re: Zincs over the side

You can always use a "Guppy" anode (or whatever) clipped to your engine block, prop shaft or rigging (as I believe that Beneteau rigs are bonded to the electrical system) and dropped over the side but that's just a Band-Aid and shouldn't be necessary. Get anodes on both your prop and shaft and barring any other issues, you should be in good shape.
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Old 21-09-2020, 09:35   #9
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Re: Zincs over the side

Ideally you need to get a silver chloride probe and connect it to a volt meter with the negative lead attached to the your engine ground. Hang the probe over the side and read the millivoltage. Should be ~950-1100 mv. If under 950mv, likely not enough anodes. Can hang additional anode attached to ground or add fixed anodes. Be aware that one can have too much anode material as well.
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Old 21-09-2020, 09:50   #10
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Re: Zincs over the side

The idea of a zinc over the side is primarily to slow down the erosion of the shaft zincs. Use scrap sacrificial zincs over the side to slow down the depletion of more expensive zincs when the vessel is at rest. Attach the sacrificial zinc to the drive line or motor.
On a fiberglass boat the hull potential should be in the 500 to 700 millivolt range [B][U]not over 900 millivolts.
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Old 21-09-2020, 10:05   #11
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Re: Zincs over the side

Quote:
Originally Posted by mark lennoc View Post
I am wondering if I could get some help with information on zincs. Particularly with zincs hanging overboard which I have seen quite a bit at marinas. Are they a good idea given unknown hazards at a marina? Where ahould a guy connect them to, engine, shaft etc? My shaft zinc seems to go quickly at the marina although with a Beneteau 373 the shaft zinc is quite small.
Any other information would be helpful.
Thanks
I have a zinc on my boat shaft and a zinc on my MaxProp which I change annually. I also put a zinc over the side, bolted/wired to my transmission, whenever I leave the boat. I do the latter even though I moor my boat to a buoy 24/7/365 (hundreds of yards from the nearest dock or boat) rather than a marina as a backup because @#$% happens. Zincs are cheap protection compared to the cost of corrosion repair and you can make your own grouper/guppy to put over the side with very little effort.

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Old 21-09-2020, 10:06   #12
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Re: Zincs over the side

I don't know how the Beneteau's are set up, but I'll mention - if you have a saildrive, they are electrically insulated from the engine, therefore you want to connect the hanging zinc to something connected to the saildrive not the engine. It'll be obvious because on Volvo Penta's for example they use these little plastic plate washers where the saildrive gearing meets the engine.


I do think these are a good idea. We moored in Fort Lauderdale for a year and have some major corrosion to the folding prop blades as well as the heads of the screws that retain the pins that keep the blades on. One screw sheared off and the others on one side all showed corrosion in the same places. There was more than one derelict boat in the marina, nearby to us. We had been changing zincs every 3-4 months, and that was not enough.. I've since gotten spare blades ($$ dammit) but am trying to get as much out of the old ones as possible..at least until I get to clear water where it will be easy to change if they break
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Old 21-09-2020, 10:31   #13
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Re: Zincs over the side

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I don't know how the Beneteau's are set up, but I'll mention - if you have a saildrive, they are electrically insulated from the engine, therefore you want to connect the hanging zinc to something connected to the saildrive not the engine.
He doesn't have a saildrive.
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Old 21-09-2020, 10:58   #14
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Re: Zincs over the side

We have a Beneteau 423 with a Maxprop and use the standard prop zinc anode. Out boat is on a mooring. We usually have to replace it once during our New England season. One reason I think they go so fast is due to the iron keel of the Beneteau. Whilethe keel should normally be encapsulated reality is that there are always a few rust spots, sometimes patches, especially on the bottom of the keel. I started using a line cutter anode from made by SALCA like this one https://anodeshack.com/beneteau-coll...lca-zinc-anode. Note it is a part made to fit the very small space between the cutlass and the front end of the prop. This seems to slow things down. We also have started turning off the negative disconnect as well as the positive when we leave the boat.


I used to put a guppy over the side, but found that it did not slow the rate of decay of the prop anode. I clipped the end of it to the backstay which I believe was all tied in to engine eventually via the mast and the VHF ground. I've intended to try this again and verify the ground.


Marinas are challenging. Improper wiring and/or boats without zinc protection make you the anode for others. But, we have problems even without being in a marina so the marina may not be the source of your problem.


This year I think we may make it through the entire season (now, I've probably jinxed us).



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Old 21-09-2020, 16:30   #15
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Re: Zincs over the side

We have a guppy and a galvanic isolator. It all helps. My 5" disc zincs are expensive and so are our prop zines ($40!)
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