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Old 12-08-2009, 11:05   #1
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Zinc Fish

Just got an email from the bottom cleaner guys saying that our Strut zinc wasn't burning and that our strut was showing electrolysis. They said we could go to West Marine and get a zinc fish which you hang over the side and wire it to the engine block. I don't know what a zinc fish is, how it would help or what it would taste like. Can someone explain?
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Old 12-08-2009, 12:00   #2
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they are marketed as a "zinc grouper", google it you'll get complete information.
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Old 12-08-2009, 12:09   #3
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They are reportedly high in heavy metals, so I would avoid baking , grilling etc. :>)However, many people hang them over the side , especially when staying in a marina due to the stray currents that can eat your metal! It can be any zinc attached to a thick wire and to the engine or shaft if your shaft has a rubber isolator... There was a Valiant 32 that sailed around the world with no zinc eating issues. It returned to Seattle, had the bottom done, a new shaft etc and was moored in a marina. A diver went down to clean the bottom after a few months and told the owner to haul it immediately. The new shaft had turned to a hollow "lace" like thing and the bronze thru hulls were powder. I actually saw the shaft... some marinas can be very bad in combo with certain boats and a specific location in the marina....
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Old 12-08-2009, 12:43   #4
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They are reportedly high in heavy metals, so I would avoid baking , grilling etc. :>)However, many people hang them over the side , especially when staying in a marina due to the stray currents that can eat your metal! It can be any zinc attached to a thick wire and to the engine or shaft if your shaft has a rubber isolator... There was a Valiant 32 that sailed around the world with no zinc eating issues. It returned to Seattle, had the bottom done, a new shaft etc and was moored in a marina. A diver went down to clean the bottom after a few months and told the owner to haul it immediately. The new shaft had turned to a hollow "lace" like thing and the bronze thru hulls were powder. I actually saw the shaft... some marinas can be very bad in combo with certain boats and a specific location in the marina....
Is there somewhere specifically on the engine I need to mount this thing? How is this going to make more of a difference than the zinc that's down there now? I'm not sure if I have a rubber isolator or not? How fast do I need to get this done? Is my boat safe right now? I noticed a bit of electrolysis on one of the through hulls the other day (white blue fuzzyiness on some of the bronze???) I wiped it off and am monitoring it. Am I going to sink?
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Old 12-08-2009, 13:08   #5
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Goto: Sacrificial Anodes (Zincs) - BoatSafe.com
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Old 12-08-2009, 13:17   #6
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From Boat Safe "The "fish" come with a copper wire already attached which is also used to hang them in the water. They have an alligator clip on the end of the wire and this should be connected to the negative bonding circuit on your boat."

Is the engine part of the negative bonding circut?
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Old 12-08-2009, 13:19   #7
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Electrolysis and corrosion are very difficult to predict well. The large additional zinc helps by giving you additional coverage. Are you in a marina and hooked to shore power? DOes a battery charger run? are your thru hulls bonded together with a wire? Actually , for your original question, the strut, you would need to clip the fish to one of the strut bolts or somehow get contact with the strut. If your strut zinc isnt corroding away, it's not working. Maybe it was put on over bottom paint of not in good contact with the zinc. Are the strut bolts exposed or glassed over? is there a bonding wire to those? You can measure stray current potential on your boat with a volt/ohm meter, or have someone do it, but they may need to get at the strut bolts to meaure that...
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Old 12-08-2009, 14:25   #8
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Electrolysis and corrosion are very difficult to predict well. The large additional zinc helps by giving you additional coverage. Are you in a marina and hooked to shore power? DOes a battery charger run? are your thru hulls bonded together with a wire? Actually , for your original question, the strut, you would need to clip the fish to one of the strut bolts or somehow get contact with the strut. If your strut zinc isnt corroding away, it's not working. Maybe it was put on over bottom paint of not in good contact with the zinc. Are the strut bolts exposed or glassed over? is there a bonding wire to those? You can measure stray current potential on your boat with a volt/ohm meter, or have someone do it, but they may need to get at the strut bolts to meaure that...
I'm embarrassed to say I don't actually know what my strut is. We are hooked to shore power and we do have a galvanic isolator installed. All of our through hulls do appear to be bonded with the ubiquitous green ground wire. We do not run our battery charger, we just let our solar array trickle charge our bank.

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you would need to clip the fish to one of the strut bolts or somehow get contact with the strut
That's what I figured. Connecting it to the engine isn't going to really do anything.

It looks like I'm going to swim under the boat to connect some fish that you can't eat to a thing I've never seen or heard of so that our strut isn't eaten by other things you can't see. I love boats.
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Old 12-08-2009, 14:27   #9
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Not familiar with your boat, but look inside the hull for some bolts that hold your strut on. I wouldnt try to clip it to the skeg in the water. Or get your diver to remove the zinc on the strut, clean the strut to bare metal under the zinc and put a new one on!! If the strut is decomposing and the zinc is not corroding, there is something wrong....
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Old 12-08-2009, 14:52   #10
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Is the strut the thing that the rudder mounted on?
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Old 12-08-2009, 15:31   #11
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It's the thing holding the back end of your prop shaft to the hull.
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Old 12-08-2009, 15:59   #12
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well....

I have assumed the strut your diver mentioned is the propellor shaft supporting strut (see the item in the pic just above the propellor...hard to see)
gave up on the pic, here's the link, scroll down... http://www.sailnet.com/forums/boat-r...bond-38-a.html
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Old 12-08-2009, 16:06   #13
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The fish is a band-aid solution until you can get the zinc on the strut to start doing its job. You need to haul out or get the diver to remove the present zinc and figure out why it is not bonding. It may be a simple matter of cleaning up any oxidation and putting it on tighter.
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Old 12-08-2009, 17:08   #14
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I have assumed the strut your diver mentioned is the propellor shaft supporting strut (see the item in the pic just above the propellor...hard to see)
gave up on the pic, here's the link, scroll down... http://www.sailnet.com/forums/boat-r...bond-38-a.html
Thanks for going to the effort of getting me that picture, I appreciate it. I have since installed the fish (you should have seen everyone looking at me in west marine). I went into the lazarrette and looked for what I thought was the strut, the big metal thing attached to the rudder and steering column. That, whatever it's called, was indeed was showing signs of galvanic corrosion (green/white pasty flaky stuff). I attached the fish to the ground wire that is attached to that thing and I am hoping for the best. In the meantime we will have a chat with our neighbors and diver. We have a guy that just moved into a boat next door that had been inactive for a long time. I am wondering if it is him using his battery charger.
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Old 12-08-2009, 21:46   #15
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Fun and games with a multimeter...

If you're feeling bored and want to entertain yourself get a digital multimeter, put it on the lowest scale, and measure the voltage difference between your fish and various metal parts of the boat.

Can get some interesting results...
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