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Old 25-11-2014, 20:04   #16
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Re: Need help finding a suitable prop anode

Old anodes are excellent to recast. There are no magic formulas for zincs. Bronze and stainless are more noble metals than zinc. so the less noble zinc is eaten before the bronze or stainless. Look up noble metals on wiki. Mac
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Old 25-11-2014, 20:25   #17
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Re: Need help finding a suitable prop anode

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Originally Posted by Hard Rock Candy View Post
There are no magic formulas for zincs.
Umm... yes there is. It's called Military Specification A-18001K and the best anodes are produced using it. Zinc anodes are an alloy of metals. They are not 100% zinc. And if you think that picking up a bunch of spent anodes out of the boatyard trash cans and recasting them is going result in an anode that meets that Mil Spec, I've got a bridge to sell you. But maybe you don't care what kind of protection your underwater metals receive.


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Bronze and stainless are more noble metals than zinc. so the less noble zinc is eaten before the bronze or stainless.
Yes, I know. Corrosion control is how I earn my living.
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Old 25-11-2014, 22:40   #18
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Re: Need help finding a suitable prop anode

Thanks for the interesting discussion gents.

The free space behind my prop is only 3/4", too little to be of any use. The idea of smelting zinc to make my own anode seems the only solution to my problem.

Some months ago I considered custom making my own prop anode, but did not know if a propane torch would be hot enough to smelt the zinc. I'll have to check it out.

fstbttms says it's a waste of time using spent anodes, but what if I bought a couple of NEW anodes and smelted them, would this be a better option?

bony
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Old 25-11-2014, 22:55   #19
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Re: Need help finding a suitable prop anode

How about coming at the problem from inside the boat?
Install a shaft brush on the inside of the boat and wire it to an external anode.

Shaft Brush
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Old 26-11-2014, 00:17   #20
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Re: Need help finding a suitable prop anode

Thanks HopCar,

That sounds like a better option. I'll have to do a bit more reading up on the subject as I know little about it. Does it have to be connected to an external anode or will the brush still do the job if I bond it to the engine ground?

bony
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Old 26-11-2014, 13:01   #21
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Re: Need help finding a suitable prop anode

bony, The shaft brush need to be connected to an external zinc. It can be placed anywhere on the hull and using a #6 piece of wire to connect the brush to a bolt inside the hull that holds the zinc. But you must make sure that any caulking you use to waterproof the holes you drill does not block the brush to zinc connection. Connect the engine to the exterior zinc also. Not your DC ground. Chuck
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Old 26-11-2014, 13:08   #22
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Re: Need help finding a suitable prop anode

As a stop gap thing, you can use a "guppie" zinc that you connect when your docked until you get a proper zinc fitted.
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Old 26-11-2014, 17:37   #23
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Re: Need help finding a suitable prop anode

I use one of these Buck Algonquin mounts for mounting my hull anode. It makes it very easy to change the zinc when I need to. A stud goes into the center hole and the zinc mounts on this. Thee internal wires fasten to the two flat head mounting bolts that go through the hull.
Item # 10zp900bp, Bronze Backing Plates for Hull Zinc On Buck Algonquin


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Old 30-11-2014, 01:47   #24
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Re: Need help finding a suitable prop anode

Sorry for the slow response, had to step out for a couple of days.

"As a stop gap thing, you can use a "guppie" zinc..."

I wondering if a guppy zinc will suffice, instead of going to the trouble of drilling holes in the hull to fit the backing plate Hopcar suggested?

I read somewhere that when you plug into shore power you become connected to all the other boats theough the shore power negative.

My boat's jetty mooring lies between a 40' wooden fishing boat and a 35' f/glass bay cruiser. The jetty has no shore power at all which means I won't be connected through the negative to the other boats so I wonder if I need to be worried about corrosion after all?
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Old 30-11-2014, 08:17   #25
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Re: Need help finding a suitable prop anode

If you have underwater metals and a 12-volt electrical system aboard, you still have to worry about corrosion.
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Old 30-11-2014, 09:12   #26
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Re: Need help finding a suitable prop anode

How was the prop protected when the boat was new? Before you restored it?
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Old 30-11-2014, 16:18   #27
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Re: Need help finding a suitable prop anode

A guppie zinc as long as it is connected properly will work as well as any other zinc of the same size.
I'd at least get one until you sort out a permanent solution, even if that is a guppie zinc.
One reason I like them is you get to see what is going on every time you pull the zinc out of the water to take the boat out, if it suddenly starts getting eaten up, you'll probably find out in time to not have major issues
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Old 01-12-2014, 14:50   #28
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Re: Need help finding a suitable prop anode

Using the left over metal in used anodes/"zincs" is just as good as melting down new anodes to suit, and yes ,you can save some money doing that. It is every bit as effective as new anodes because it is unused alloy, just as it came from the manufacturer, despite what fstbttms claims. For the last fourty years, I have been re-melting old anodes and pouring them on commercial boats with 24" - 48" propellers, usually using a selection of tinned tomato cans (3"-5" diameter), with excellent results.In your case you may find it difficult to get a large enough quantity of zinc on to last an entire season but you can back it up with a shaft brush and external zinc anyway. A regular handy-man's propane torch won't give you enough heat to melt zinc, you need the extra volume a tiger torch produces.
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Old 01-12-2014, 17:51   #29
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Re: Need help finding a suitable prop anode

Look at the "Perry Prop Nut" on the Boat Zinc web site. The Zinc goes over the first nut and is held on with the lock nut.
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Old 01-12-2014, 21:39   #30
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Re: Need help finding a suitable prop anode

Yes, those "cup"-type anodes are what a lot of larger installations use but unfortunately, in this particular case there isn't room for a second nut. The biggest problem with any of these bolt-on zincs is the fact that the zinc ablates around the fastener at the same rate it ablates on the general surface and often the zinc gets pitched off prematurely and you lose its protection unknowingly. A shaft-brush wired to an external anode is good, but relies on good wire-eye connections(usually in poor conditions) and can be undone by oil contamination on the shaft contact area.It needs to be looked at regularly, and it is seldom in an easy to access area. Just a note on brushes- many boat owners here make their own using an old chromed salmon flasher and a copper chore-girl, they work actually better than the carbon or metal-brushes and can be re-brushed with a new copper pot scrubber in a NewYork minute!
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