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Old 16-10-2014, 14:17   #1
F51
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Unusual prop zinc anode

My prop has an acorn-shaped zinc on the very end of the shaft. I'm looking for a replacement. It has a hex cut out in the big end to fit over the prop nut, and about a 3/8" hole in the pointed end for the attaching screw. I have looked at the shipyard's catalogs and can't find the correct size. The shaft is 1-3/4 inch diameter. I don't know the prop nut size, but it holds a 25 x 20 LH Michigan prop. It is a Formosa 51. Anybody know where to source such a beast? Thanks.
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Old 16-10-2014, 14:22   #2
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Re: Unusual prop zinc anode

BoatZincs.com (978-841-9978) – The Online Superstore for Zinc Anodes
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Old 16-10-2014, 22:19   #3
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Re: Unusual prop zinc anode

A 1 3/4" shaft takes a size "G" anode.
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Old 17-10-2014, 04:21   #4
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Re: Unusual prop zinc anode

Thanks for the link. That helps explain the pitting on my prop. I don't have enough clearance for a shaft zinc. A prop shaft nut zinc looks good. never knew such an animal! Another great idea to be in this forum.
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Old 17-10-2014, 05:25   #5
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Re: Unusual prop zinc anode

I have the same type anode only the shaft is 1 inch. One issue i kepted having was the anode would pit in around where the bolt holds it on and the anode would become loose and rattle. The fix was to put a bit of heat shrink on the bolt just where it passes through and contacts the anode. Hasn't happened since doing this. Don't know if anyone else has experianced this, Thought i'd pass it on!!!
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Old 17-10-2014, 11:51   #6
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Question Isolation?

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Originally Posted by nicholson31 View Post
I have the same type anode only the shaft is 1 inch. One issue i kepted having was the anode would pit in around where the bolt holds it on and the anode would become loose and rattle. The fix was to put a bit of heat shrink on the bolt just where it passes through and contacts the anode. Hasn't happened since doing this. Don't know if anyone else has experianced this, Thought i'd pass it on!!!
I'm new to this subject, but does heat shrinking the contact point to the anode insulate/isolate it, voiding its usefulness? Or is there another point where the anode contacts the shaft to draw the galvanic reaction? At the prop nut?

I know loosening from the inside is a problem w/ these kinds of anodes.
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Old 17-10-2014, 12:35   #7
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Re: Unusual prop zinc anode

The screw attachment is not the only contact point for this style of anode. It mounts on a cone-shaped nut and much of the nut is in contact with the anode.
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Old 17-10-2014, 14:30   #8
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Re: Unusual prop zinc anode

As fstbttms said there is plenty of contact surface between the anode, nut and shaft. I considered that same question though before adding the heat shrink.
I examined the shaft on haul out and there is no pitting or corrosion. Finally a cheap fix, not too many of them!!!
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Old 07-11-2014, 21:22   #9
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Re: Unusual prop zinc anode

While you are on this subject of propeller nut anodes; ....never had seen these till I bought this other boat.
Tried to find online, some picture explaining how the 3 bladed propeller goes onto a 1" tapered shaft.
I guess it has a regular hex nut behind the prop, then comes a fairly thick washer, then the tapered nut ( what are those slots for?) , then the acorn type zinc anode just slides on top of that tapered nut, then this zinc is held in place with a screw at the center end of the cone.
Is there a cotter pin to hold the nuts and end screw from spinning off?
What keeps that small end screw from unscrewing?
My engine turns clockwise when looking at the crankshaft pulley. Perkins 4.108.
Are these prop nuts screwed 'righty-tighty', (the regular way) and that keeps them from unscrewing?
Did not remember seeing a cotter pin or being wired together.
Could not find pictures or explanations so as to be prepared to replace the missing zinc when I get to dive under.
Can any of you explain how the propeller and the zinc is held in place?
Thank you all.
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Old 08-11-2014, 06:14   #10
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Re: Unusual prop zinc anode

Quote:
Originally Posted by slowpoker View Post
While you are on this subject of propeller nut anodes; ....never had seen these till I bought this other boat.
Tried to find online, some picture explaining how the 3 bladed propeller goes onto a 1" tapered shaft.
I guess it has a regular hex nut behind the prop, then comes a fairly thick washer, then the tapered nut ( what are those slots for?) , then the acorn type zinc anode just slides on top of that tapered nut, then this zinc is held in place with a screw at the center end of the cone.
Is there a cotter pin to hold the nuts and end screw from spinning off?
What keeps that small end screw from unscrewing?
My engine turns clockwise when looking at the crankshaft pulley. Perkins 4.108.
Are these prop nuts screwed 'righty-tighty', (the regular way) and that keeps them from unscrewing?
Did not remember seeing a cotter pin or being wired together.
Could not find pictures or explanations so as to be prepared to replace the missing zinc when I get to dive under.
Can any of you explain how the propeller and the zinc is held in place?
Thank you all.
There is no washer and/or additional nut, only the cone-shaped nut that accepts the (in your case) "C" anode. The nut has slots in the cone portion of it so that a cotter pin can be installed through it and the shaft. There is no cotter pin through the anode. The anode is held on (as you surmised) by a right-turning machine screw and lock washer arrangement, nothing more.

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Old 08-11-2014, 15:45   #11
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Re: Unusual prop zinc anode

Thank you, Fstbttms, for the fast and clear reply, ......just as the work you do!.
Slowpoker.
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