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dadio917
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Discussion Starter #1
what do you guys use?

Someone told me put blue thread lock on and let it cure in air before installing underwater.
 

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Master Mariner
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Never heard of any such thing. Zincs come with SS Allen screws and I've never had one come loose before the zinc has deteriorated so much that the screw is useless.
Save your money and time.
 

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Dirt Free
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2,654 Posts
The thread lock on the contact surface may insulate the anode rendering it useless. If you do use it (I never have), make sure it's confined to the screws
 

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dadio917
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326 Posts
Discussion Starter #4
thanks for the responses.

I should have added that I just switched props and the old zinc was held on by 3 plastic fasteners. the new one is one stainless screw...hence my question.

the prop came with all its fasteners pre-coated with a thread loc for installation underwater.
 

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several of the anode brands come with the screws with the thread lock pre coated on the screws . can't hurt
 

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After you've put the zinc on coat the screw area with nail polish.
 

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Whatever is avaliable from your wife, daughter or girlfriend.
 

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We had a tailcone zinc for our MaxProp disappear one year (out of the 22 yrs we’ve owned this boat) and the 3 screws were also gone. The prop was uncoated that year and showed noticeable pitting, which led to a MaxProp overhaul at PYI. Hadn’t had a problem with the zinc before or since.

For quite a few years now, we’ve been coating the prop with Pettit zinc spray, sanding the prop and zinc where they contact, coating the screws with the blue stuff, and coating the area of the zinc around the screw heads with nail polish. The attached photo shows you what the prop looked like a few weeks ago after haul out and pressure washing by the yard. Must be about 98% of the zinc is left.
 

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dadio917
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326 Posts
Discussion Starter #10
I asked boatzincs.com...here is their answer:

Thread locker is something we tell folks to consider only if they're having a specific problem with the bolt rocking out. Otherwise, it's probably not necessary.

If you would like to use it, we like Vibra-Tite VC-3 (https://www.boatzincs.com/vibratite-specs.html). As with any thread locker, a little goes a long way. We recommend thinly coating the tip of the bolt, letting it dry, and then installing.
 

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Cruiser
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what do you guys use?

Someone told me put blue thread lock on and let it cure in air before installing underwater.
I wouldn't use any threadlock as that might preclude being able to change your anodes underwater. [Often some heat is needed to break even the Blue threadlocker loose...]

Here is the Marine How-To article on anode best practices...

Cheers! Bill
 

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This tack doesn’t require a sledgehammer. Clean the shaft well, tighten the screw firmly. Don’t think anything else is necessary, other than periodic inspections, which would not be avoided by thread lock.

If an anode is not decaying very much, it may not be working, due to being accidentally electrically isolated.
 

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This tack doesn’t require a sledgehammer. Clean the shaft well, tighten the screw firmly. Don’t think anything else is necessary, other than periodic inspections, which would not be avoided by thread lock.

If an anode is not decaying very much, it may not be working, due to being accidentally electrically isolated.
I’ve been using blue threadlock for several years after losing a prop zinc and all three screws several years ago. No problem removing the screws to install a new zinc. Before this I simply tightened the bare screws.

I always sand the bronze and mating zinc surfaces before installing the new zinc. However, I have been using the Pettit zinc spray on my MaxProp for about 4 or 5 years now with fantastic results as shown in the attached photo, taken after haulout earlier this month. The only treatment was the typical power wash by the boatyard. My guess is that 95+% of the tailcone zinc remains (although the nail polish around the screw heads is gone.)
 

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f...... maxprop anodes are notorious for rapid decay. I worry that yours isn’t decaying enough to demonstrate that it’s working well.
 

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f...... maxprop anodes are notorious for rapid decay. I worry that yours isn’t decaying enough to demonstrate that it’s working well.
The reason for using a prop zinc is to protect the prop from galvanic corrosion. As you can see in the thumbnail in post #14, the prop is not corroding during the season. The zinc coating on the prop is part of the solution. There is some pitting of the zinc coating which may be due to cavitation. In any case, the bronze is protected and that is the point.

I’ve been using Camp zincs (about half the price of the zinc PYI sells) for quite a few years and they work for me. Before I coated the prop there was significant erosion of the prop zincs. One year the zinc disappeared and I had significant pitting of the bronze. I sent the prop back to PYI for remanufacture. After that I began using the Pettit zinc paint, and there has not been any corrosion of the bronze and the tail cone zincs remain substantially intact after the season. I still replace them in the Spring, but that is probably unnecessary.
 

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Dirt Free
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In any case, the bronze is protected and that is the point.

One year the zinc disappeared and I had significant pitting of the bronze.
Just to keep the record straight ... it is extremely unlikely that anyone on this forum has a "bronze" propeller, they are very rare and hideously expensive. A real bronze propeller is not often bothered much by galvanic corrosion.

What we have are "manganese bronze" propellers and this is actually a bit of a misnomer as this material contains 35 - 38% zinc which puts it squarely in the "brass class".
 
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I struggle a bit to think the amount of zinc in the paint is substituting for the amount of anode galvanic corrosion that typically occurs. The paint is designed to be a barnacle protectant and sluff off. Early signs of prop de-zincification are discoloration of the metal, before pitting. Harder to identify when painted.

Not catastrophizing or criticizing, just perplexed.
 

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I struggle a bit to think the amount of zinc in the paint is substituting for the amount of anode galvanic corrosion that typically occurs. The paint is designed to be a barnacle protectant and sluff off. Early signs of prop de-zincification are discoloration of the metal, before pitting. Harder to identify when painted.

Not catastrophizing or criticizing, just perplexed.
I hand sand to remove the old paint before reapplying the new paint and haven’t see any indication of dezincification. The prop is now 27 yrs old and is holding up well since I started using the zinc paint about 6 or so years ago. BTW, it really works well to prevent barnacles, as you can see from the photo in post
#14.

It also helps that there is not a lot of underwater dissimilar metal on my boat and that the boat is not kept at a marina with the potential for stray current caused by nearby boats.

My experience is offered for your information: I am not pretending to explain the electrochemical process as an expert.
 

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I bought a can several years back and never applied. I should try it. If it truly supplements the anode, that would really be terrific. My max prop anode disappears in a season, but I can manage one full season with the shaft zinc. I think the dissimilar metal issue for all of us is the shaft vs prop.
 
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