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Old 02-06-2015, 07:52 PM   #21
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Originally Posted by psneeld View Post
I'm a believer in shaft brushes...have installed them on my last 3 liveaboards and the equalization of zinc depletion has evened out and become satisfactory and manageable for boats left in the water all year round.
We don't have one but thinking about it. Any suggestions or pictures?
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Old 02-06-2015, 08:02 PM   #22
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There are commercial ones available...

I made mine out of a piece of bent, scrap aluminum with a one inch by one inch piece of old zinc that came off of an outboard (grabbed several for spares at the marina recycling bin). The zinc already had a bolt through the middle so I just added a jumper wire from that bolt to my bonding runs.

The aluminum arm is attached to a stringer with only one pivot screw but is left loose so the weight of the zinc keeps the arm on the shaft.

Sorry no pics..but there are nice copper/bronze ones available on the net ND plenty of pics if you google.

Mine is buried under the aft head sink so pics would be a pic but will if you like.
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Old 02-06-2015, 08:46 PM   #23
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Our boat is fitted with the Ever-Guard system where everything is bonded to two large plate zincs on the transom and a reference zinc under the hull. Any additional zincs will negate the effect of the system. Don't believe it but we were told by the yard that once a zinc is out of the water it is no longer useable. Anyone else ever heard that? I'm talkin' salt water here.
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Old 02-06-2015, 08:48 PM   #24
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I called Propellor Solutions in San Diego but they never called back Looks like we'll splash as is.
I don't get this. Your yard identified a problem and you drove 90 miles and confirmed it might be a problem. You seek professional advice for a sound opinion. They fail to respond so you ignore the problem and splash the boat? What am I missing here?
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Old 02-06-2015, 08:49 PM   #25
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..Don't believe it but we were told by the yard that once a zinc is out of the water it is no longer useable. Anyone else ever heard that? I'm talkin' salt water here.
They sit awhile on shop shelves before they get sold and fitted.
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Old 02-06-2015, 08:49 PM   #26
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Shaft brushes are good, but there are lots of opportunities for poor connections from shaft all the way back to transom zinc. Shaft zincs right in front of strut have a better chance of making a good connection.

Best is to have both.

OP photos did not seem to show any shaft zincs in view.
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Old 02-06-2015, 09:43 PM   #27
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I still had the stainless arms left to our shaft "brushes". I took an electric forklift motor brush (same as a starter brush) and epoxied it to the arm. I drilled a hole in the arm, and used a small bolt to fasten the pigtail from the brush to the bonding wire. Has worked fine (I guess) for a couple of years. Will shoot a pic Sunday when I go to the boat.


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Old 02-07-2015, 12:05 PM   #28
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I am not about to pay lay days to the boat yard while I find a prop shop willin' to do the work.
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Old 02-07-2015, 12:30 PM   #29
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Did you put shaft zincs on?
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Old 02-07-2015, 12:45 PM   #30
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Greetings,
Mr. F. Did you use conductive epoxy? If not, have you checked the continuity between the "business end" of the brush and your grounding system?
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Old 02-07-2015, 01:47 PM   #31
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On my previous boat I rigged a wire w a clip on one end for the propeller shaft and a piece of zinc on the other. Would attach it to the shaft (when in harbor) and put the zinc over the side and submerged several feet. Would need to remember to remove the clip when getting under way. I now use the "zinc bullets" that SCOTTEDAVIS posted and wonder if the over the side wired zinc would help save the "bullet"? Now I've got the "Barnacle Buster" coating on my prop. I know one can get over zinced.
I drilled a hole in the rudder to extract the prop shaft and plugged it w the piece that came out w the hole saw using three carriage bolts.

Re Peter B's comments I replaced the original prop on our 40 yr old boat just 2 or 3 years ago mostly because I wanted the style of prop in the picture.
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Old 02-07-2015, 03:08 PM   #32
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My shipwright works on a lot of the commercial boats in Steveston. While they are in the hard getting work done, he pours molten zinc into a "sandwich mold" around the prop hub. The molten zinc infiltrates all of the "prongs" on the hub. A tiger torch is used to remove the spent zinc. He goes about the yard recycling the old zincs as part of this process.

I used a ready-made prop "bullet" last time, but I think I'll see if Murray can "molten zinc" thing next time.


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Old 02-07-2015, 07:12 PM   #33
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Greetings,
Mr. F. Did you use conductive epoxy? If not, have you checked the continuity between the "business end" of the brush and your grounding system?

RT, good question. Actually the "leads" are embedded in the brush, so I felt that having them fastened to the bonding wire with a bolt and nut would assure continuity.
Friday the yard finished the bottom paint and replaced all zincs except for the prop shaft 1 3/4" ones that are ordered for Monday. He assured me he would sand/ polish the paint off before mounting the zincs. I never mentioned to him I had the shaft brushes- figured the bolt on's would give some added protection.
I actually don't know how to determine if my bonding system is doing the job other than what appears to be normal wear patterns on the block zinc.
Wouldn't mind some advice on how to do it.


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Old 02-07-2015, 07:34 PM   #34
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RT, good question. Actually the "leads" are embedded in the brush, so I felt that having them fastened to the bonding wire with a bolt and nut would assure continuity.
Friday the yard finished the bottom paint and replaced all zincs except for the prop shaft 1 3/4" ones that are ordered for Monday. He assured me he would sand/ polish the paint off before mounting the zincs. I never mentioned to him I had the shaft brushes- figured the bolt on's would give some added protection.
I actually don't know how to determine if my bonding system is doing the job other than what appears to be normal wear patterns on the block zinc.
Wouldn't mind some advice on how to do it.


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Get a multimeter, switch it to ohms, put one lead on each metal you are concerned about and measure the resistance. You should get a reading of 0.05 or less, 0.00 is best. The higher the reading the more resistance (less continuity).
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Old 02-07-2015, 08:07 PM   #35
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greetings,
Mr. Fork. Ahhhh....Re-read your post. I had missed the mention of the pig tale-apologies...
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Old 02-07-2015, 08:38 PM   #36
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My shipwright works on a lot of the commercial boats in Steveston. While they are in the hard getting work done, he pours molten zinc into a "sandwich mold" around the prop hub. The molten zinc infiltrates all of the "prongs" on the hub. A tiger torch is used to remove the spent zinc. He goes about the yard recycling the old zincs as part of this process.

I used a ready-made prop "bullet" last time, but I think I'll see if Murray can "molten zinc" thing next time.


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Zincs are comprised of other ingredients (alloys) when they work they give up ingredients, melting down whats left will not give you a new good replacement.

I would not use a zinc re-melt, I think the China zincs are made better and they are junk.

" Canada Metal zincs are composed of an alloy that meets Mil-Spec MIL-A-18001 for sacrificial anodes. This alloy is mostly zinc, but with measurable concentrations of cadmium (~0.1%) and aluminum (~0.25%). The additional cadmium causes the anode to erode from the surface inward, which causes a ''sandblasted'' appearance to the surface. When the anode is almost dissolved, it needs to be replaced."

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Old 02-07-2015, 08:50 PM   #37
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I'm not so sure that's the case, Scott, otherwise there'd be a lot of unhappy fishermen about! :-) it's a pretty common procedure around the commercial waterfront. One would think that otherwise there would be a problem with oxidation of a lot of props out there. Murray would have learned this procedure from veteran shipwrights 35 years ago when he apprenticed with Canadian Fish. I've watched him do this and the slag separates from the liquid metal.


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Old 02-07-2015, 09:02 PM   #38
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Like many things I life...there's high grade and low grade....

My bet is smelting of used zincs may work.....but it's like spraying oil on an old road instead of new asphalt. It may work...but just barely.

Smelting new zinc alloy would be OK....but is it new or old, depleted zincs?

....have to agree that as a zinc depletes.....what is left isn't what you started with....I think but could be wrong..
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Old 02-07-2015, 09:35 PM   #39
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Not so pretty in pink...

Okay, so think about this a bit more....

You've got the best zinc in the world. Maybe it's got a bit more Cadmium or Aluminum or whatever, but...it's held on...with a screw?!?! It fits fine when you put it on but next year when you take it off, is it secure? How many loose zincs have you seen when you take them off? Now compare that to a process where molten sacrificial anode is pored around the prongs on the hub of the propeller. It takes a tiger torch to remove the material.

Don't know for sure but I think I'll trust the shipwright.


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Old 02-07-2015, 09:45 PM   #40
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Get a multimeter, switch it to ohms, put one lead on each metal you are concerned about and measure the resistance. You should get a reading of 0.05 or less, 0.00 is best. The higher the reading the more resistance (less continuity).

Boat poker, sorry I don't quite follow. I know if I want to be sure my prop shaft has continuity through the brush and to the bonding wire I would measure resistance between the shaft and the bonding wire. Is that what you mean? I wonder if there is an easy way to be sure there is minimal resistance from say- the prop shaft to the big zinc block ?


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