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post #21 of 36 Old 12-12-2016
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Re: Propeller pitting

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Originally Posted by Minnewaska View Post
Would this be a submerged pump, more than a diaphragm with a hole pickup, or both?

I supposed a remote float switch, for either, is wet virtually 100% of the time.
Type of pump is irrelevant. The issue is DC current exposed to bilge water through failed insulation, short circuits, bad connections etc. whether it's at the pump or the float.
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post #22 of 36 Old 12-12-2016
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Re: Propeller pitting

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Originally Posted by Minnewaska View Post
The replacement anode screws, from PYI, do come with holes that I presume one could thread safety wire through. I've never attempted it. Seems it would introduce one more dissimilar metal to the mix and perhaps impact balance.

https://store.pyiinc.com/products/sc...ant=4653659457
Imbalance would be insignificant due to such possibility of wire or cotter pins being near the center of rotation of the assembly. Even if such were installed at the extreme of rotation - the edges, their mass is insignificant in comparison to the whole. An eccentric mass of a gram or less is not going to change the 'natural frequency' of the entire system, just like a single barnacle attached near the center of rotation will be 'benign' vs. rotational imbalance / natural frequency of the assembly.

The dissimilarity of composition ... that what the anode is for. Remember that most metals are alloys that have distinct microscopic dissimilar metals as 'grains' ... macroscopic/microscopic little 'islands' or 'globules' of dissimilar metals throughout the metal's crystalline structure.
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post #23 of 36 Old 12-12-2016
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Re: Propeller pitting

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Originally Posted by RichH View Post
Imbalance would be insignificant due to such possibility of wire or cotter pins being near the center of rotation of the assembly. Even if such were installed at the extreme of rotation - the edges, their mass is insignificant in comparison to the whole. An eccentric mass of a gram or less is not going to change the 'natural frequency' of the entire system, just like a single barnacle attached near the center of rotation will be 'benign' vs. rotational imbalance / natural frequency of the assembly.

The dissimilarity of composition ... that what the anode is for. Remember that most metals are alloys that have distinct microscopic dissimilar metals as 'grains' ... macroscopic/microscopic little 'islands' or 'globules' of dissimilar metals throughout the metal's crystalline structure.
Just to expand on what RichH is saying (I think ) ..... many metals can suffer from galvanic corrosion without outside influence due to dissimilar metal grains within the whole. This seems particularly true in metals from Chinese foundry's, not known for the purity of their product.

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Re: Propeller pitting

BoatPoker -- totally agree.
Precise quality control during the purity of melting/heating/pouring/cooling/heat treating, etc. process' is vital for grain size and internal distribution (stratification) etc. etc. etc. The asian red metal foundries especially still dont seem to have the total developed techniques that ensure 'consistency' and uniformity of the original developments, formulations, etc.

This is especially true in the case of asian-made non-de-zincing (DR/DRZ) brasses, etc., etc.!!!!
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post #25 of 36 Old 12-12-2016
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Re: Propeller pitting

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Originally Posted by Minnewaska View Post
The replacement anode screws, from PYI, do come with holes that I presume one could thread safety wire through.
No, they don't.

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Re: Propeller pitting

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No, they don't.
I will stand corrected, until I get back to the boat (if I even remember by then). I swear I have a set with the hole. May be aftermarket.

Nevertheless, I don't think they are necessary.


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post #27 of 36 Old 12-12-2016 Thread Starter
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Re: Propeller pitting

The red in the bolt holes appears to be ink, like from a Sharpie pen. I think the previous owner did that, because he left me a number of spare anodes and they all have that red in the bolt holes. I have never used Lock-Tite - doesn't seem necessary for the cone anode. I don't have an anode on the short amount of exposed prop shaft forward of the propeller. I'm not sure one would fit there but I'd have to have it in front of me to know for sure. There is another anode at the base of the rudder skeg (see before and after photos), and I put a magnesium one on there as well.

Boatpoker's comment about electrical contact is very interesting... I recall using a wire brush to clean off debris after removing the previous anode (zinc, which was half gone), but maybe I didn't get enough off. If a wire brush isn't enough to get it clean, what would be better? I'll get my multimeter and check the resistance in the meantime.

Regardless, it looks like I'm going to end up sending the prop in to PYI to get it overhauled...
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post #28 of 36 Old 12-12-2016
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Re: Propeller pitting

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Originally Posted by kbbarton View Post
The red in the bolt holes appears to be ink, like from a Sharpie pen. I think the previous owner did that, because he left me a number of spare anodes and they all have that red in the bolt holes.
The red may be fingernail polish painted on the zinc to slow its corrosion in the painted area. I (for a while) painted mine under the bolt heads so that the zinc there would not corrode away and leave the bolts lose to possibly back out.

Try Googling zinc anode fingernail polish.
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post #29 of 36 Old 12-12-2016
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Re: Propeller pitting

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Originally Posted by kbbarton View Post
The red in the bolt holes appears to be ink, like from a Sharpie pen. I think the previous owner did that, because he left me a number of spare anodes and they all have that red in the bolt holes.
The red might be nail polish. I use nail polish AFTER installing the zinc and screws. It is applied to minimize zinc loss near the screw heads so as to assure the zinc stays attached as long as possible. You may not want the red stuff to insulate the screw head from the zinc.
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post #30 of 36 Old 02-03-2017 Thread Starter
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Re: Propeller pitting

After consultation with the folks at PYI, looks like I am going to send the propeller in to be reconditioned. I found a handy video on disassembling a three-blade Classic. I need to de-grease it before shipping it to PYI. Anyone have a recommendation for how I can do that? I know industrial de-greasers are extremely toxic and nasty to work with, but I'm curious what my fellow sailors use on their boats.
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