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Old 12-23-2017, 06:01 PM   #1
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Looks like I lost my prop shaft zinc (video)

I know many people have mentioned shaft zincs can come off so I thought I'd check all my zincs with my GoPro. Sure enough, shaft zinc gone. Check those zincs!

https://youtu.be/P2qXnNg9Xyc
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Old 12-23-2017, 06:53 PM   #2
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My diver checks my zincs. Replaced many but never lost one. Not yet anyway.
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Old 12-23-2017, 07:17 PM   #3
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Quote:
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My diver checks my zincs. Replaced many but never lost one. Not yet anyway.
That's the thing though... if a zinc is just gone completely, especially on a shaft or thruster, it may very well have just worked itself off with all the motion.
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Old 12-23-2017, 07:20 PM   #4
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I have not heard of it just working itself off from motion. I’ll have to ask my diver if that sort of thing is common.
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Old 12-23-2017, 09:40 PM   #5
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I changed years ago from egg shafed shaft zincs to Donut shaped, as I had never seen the egg shaped ones still there on teh annual haulout. The donut shapes held on lots better. In the last few years the egg shapes have a different attachment method that seems to work. I have had them hang on for over a year in the last three haulouts.
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Old 12-24-2017, 07:41 AM   #6
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Originally Posted by koliver View Post
I changed years ago from egg shafed shaft zincs to Donut shaped, as I had never seen the egg shaped ones still there on teh annual haulout. The donut shapes held on lots better. In the last few years the egg shapes have a different attachment method that seems to work. I have had them hang on for over a year in the last three haulouts.
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Old 12-25-2017, 03:43 PM   #7
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I have not heard of it just working itself off from motion. I’ll have to ask my diver if that sort of thing is common.
Not particularly common but certainly possible if installed incorrectly or left on too long.
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Old 12-26-2017, 08:09 AM   #8
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You have to bang them tight with a hammer, then re-tighten the bolts a few times when installing them. That should keep them on at least until they erode far enough to loosen up the bolts again. Not sure how that works if replacing them in the water.
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Old 12-26-2017, 10:38 AM   #9
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You have to bang them tight with a hammer, then re-tighten the bolts a few times when installing them. That should keep them on at least until they erode far enough to loosen up the bolts again. Not sure how that works if replacing them in the water.
That's what we always did and in the water. We'd mount the zinc and tap with a hammer, retighten the Allen screws, turn the shaft 180 degrees and do it again and repeat. We never lost a zinc.

When we sold our ChrisCraft, the new owner changed the shaft zincs during the survey. One month later, he called and asked if the transmission ever made a funny noise in reverse. He hadn't set the shaft zinc and it slid up the shaft to the hull in reverse.
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Old 12-26-2017, 11:46 AM   #10
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This is somewhat application specific, we cruise at 23 knots and by the end of the season to have a zinc slide down or disappear is not all that uncommon. Displacements speeds I would guess it doesn't happen much.
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Old 12-26-2017, 11:54 AM   #11
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This is somewhat application specific, we cruise at 23 knots and by the end of the season to have a zinc slide down or disappear is not all that uncommon. Displacements speeds I would guess it doesn't happen much.


It happened to us.
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Old 12-26-2017, 11:55 AM   #12
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After you have installed them, mask off the area where the screws are located and paint the thin area with some type of paint (I use Tremclad) so that the thin area will not deteriorate too quickly. Still plenty of exposed zinc but the zinc will not come off when it does its job and the screws have no "meat" left to hold together. They will stay on much longer and therefore do their job much longer.

If you're using a diver, paint it first.
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Old 12-26-2017, 12:10 PM   #13
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I learned years ago to do several things.
Light hammering is needed to set the zincs on the shaft. Tighten the screws as described above rotating the shaft to get them even and to set each zinc half.. The screws will not pull the zincs on to the shaft.

I might try a big C clamp to speed the initial setting.

Last but not least to ensure proper electrical contact the metal mounting surfaces are sanded bright, both zinc and the surface it is mounted to.

I also use SS flat washers under the screw heads. Sometime needs a bit of playing, Dremel, to get them to fit over the screw and then into the recess.

The screws are Allen heads and that head is small. THey were designed, the Allen heads, for use in alloy , hard steels where minimal size is needed. The larger standard hex head would be a problem and of course the sockets would make the recess even larger yet.

Zinc is a soft metal and the tension will soon be lost unless the load is spread out a bit more. I also , when needed, went and bought longer screws as some times the screws were simply not long enough to grab properly. And yes, I buy good zincs.

Between the hammering and the washers I stopped losing zincs.

I agree that a fast planing boat might be more likely to loose a zinc but it is also from my fast planing boat that I figured the above out and once sorted out even on that boat I lost NO more zincs.


Xsbank: Good tip about the paint.
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Old 12-26-2017, 12:20 PM   #14
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Thanks. Here's an old photo I took:
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Old 12-26-2017, 12:44 PM   #15
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Here is a trick to extend the life of prop shaft zincs, but particularly the expensive zincs on feathering props like the MaxProp:

Before you install, take some of your wife's fingernail polish that she no longer likes (every wife goes through colors and shades ;-) and paint the area around where the screws seat. This will keep that part of the zinc from wasting and keep it from falling off prematurely.

Having said that, if the metal in your zinc is half gone, it is time to replace it.

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Old 12-26-2017, 03:13 PM   #16
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[QUOTE=djmarchand;620513]Before you install, take some of your wife's fingernail polish that she no longer likes (every wife goes through colors and shades ;-) and paint the area around where the screws seat. This will keep that part of the zinc from wasting and keep it from falling off prematurely.

David[/QUOTE

You are the third person I have heard that from. The other two were a diver in South Fl. and a diver in NC while we were looping.
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Old 12-26-2017, 08:27 PM   #17
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I guess not everyone reads all of the thread, either that or there is an echo in here...
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