Getting really tired & annoyed of losing my prop anode

[baz]

Subject: Getting really tired & annoyed of losing my prop anode

Had my underwater anodes checked yesterday and by golly the complete prop anode was missing along with its retaining bolt. It was replaced July 17, 2019. This means just under 4 months from it being replaced to finding it gone.

I really don't understand this, primarily as the retaining bolt was missing. The retaining bolt is screwed to the prop's locking nut, so even if the anode has corroded sufficiently enough to simply slide off the retaining bolt, the bolt should still be left. The bolt is coated with something like blue loctite and that should be sufficient for hold the bolt.

So, either the bolt wasn't tightened correctly on July 17, or for some other reason the bolt fell off.

I know the prop anode is the one under water anode that corrodes the fastest, but this issue is worrying.

Do others who have lost their prop anode also see that the retaining bolt was missing also ?

Just maybe there's an underwater burglar in my area. :lol:

 

[lproulx]

Same experience on 21ec. Puzzling.

 

[sjreib]

Barry,
I’m in the Edmonds marina and have never lost a prop anode on my C28 or current C30CB. Double J diving replaces my anodes about 3 times each year depending on wear. I strongly suspect the bolt securing the anode was not tightened properly.

Steve
Island Time

 

[Red Raven]

Hi Barry,

I have found that the normal amount of thread locker (the blue stuff) is not sufficient for this application. I coat the bolt completely and let it dry completely before installing the anode and that still barely seems to work. You are correct that most the other solutions are focused on addressing the lost anode with the bolt in place. First, you have to secure the bolt. Tightening it against the anode regularly helps but only if you do it at a rate faster than the anode wear. Relying on pressure against the decaying anode material to secure it presents a challenge.

They make a “red” thread locker that is designed for permanent application. I’m thinking of trying it. I suspect it is not really as permanent as they say. For example, 3M 5200 sealant/adhesive is supposed to be for “permanent” applications only but I use it exclusively above and below the waterline.

Curt

 

[baz]

Barry,
I’m in the Edmonds marina and have never lost a prop anode on my C28 or current C30CB. Double J diving replaces my anodes about 3 times each year depending on wear. I strongly suspect the bolt securing the anode was not tightened properly.

Steve
Island Time

I'm in Port of Edmonds also (have been since 2008) and I have the Double J Diving service as well since 2008, and yesterday and Jorge said the only explanation he could muster up was that maybe he didn't tighten the bolt sufficiently. Given this, it will very interesting to see if the prop anode is still there in 3 to 4 months from now.

BTW... for my previous R-25 Classic and R-21 EC I never lost the prop anode.

 

[Wee Venture]

I know I’m flying in the face of common practice here, but my understanding is that Loctite products are not designed to work the way we are trying to use them - namely, to put a liquid coating on the threads, let it dry, and then take it underwater to screw the fastener in. Here is a quote from the Loctite website:

“Anaerobic adhesives and sealants were developed by the founder of LOCTITE Corporation, now Henkel Corporation, in 1953....Anaerobic adhesives and sealants are resins that convert from liquid to a tough structural solid in the absence of air and the presence of metal.”

What I take away from this is that the product is designed to be applied to metal threads (usually male) and, while it is still liquid, the item is to be mated with its female threaded counterpart, thereby permitting liquid contact to both mated metal surfaces and sealing out air. I believe in its liquid form it flows into minute irregularities in the metals and upon curing, locks them together. If you let it dry before you screw them together, and if you let it dry in air, this will not happen.

I think there may be a product that is intended to be used as we are trying to do, but I haven’t yet figured out what it is.

 

[baz]

John: Are you speculating/suggesting that the loctite is not securing the bolt sufficiently and as a result of the prop's rotation, that presumably spins the anode at same RPM, that this can in fact cause the anode's retaining bolt to unscrew resulting in the anode dropping off ?

Let's see now, I assume the bolt screws in with clockwise rotations and for the above to happen then the prop needs to be rotating counter clockwise and with the friction between the anode aft end and the bolt head to be enough to cause the bolt to unscrew. Woweee.... that is quite a thought which needs to be examined further to see if it has any merit. 😱

So question to others: Standing at the transom and looking at the prop, which way does it rotate (clockwise or counter clockwise) when the boat is being moved forward ? I suspect the prop rotates clockwise to move the boat forward.

For most boats I suspect 99% of then time the boat moves forward and for 1% is moves backwards.

In my case I always move backwards into the fairway when leaving my slip as I'm always bow in.

 

[cal & pam]

I have a 2009 R-25 Classic and no longer loose prop zincs. My solution was to grind down the head of a SS bolt so that it can be screwed into the inside of the prop nut and not bind on the end of the prop shaft. When the prop zinc is installed over the prop nut it is secured in place by a fender washer, lock washer, and two nuts jammed together.

 

[baz]

Cal: I'm still trying to understand why the traditional way of securing the prop anode with a retaining bolt that screws into the prop nut (and having its head to keep the anode in place) can unscrew.

What means do you use to secure your SS bolt (with its head ground down) in the prop nut so it cannot unscrew ?

 

[cal & pam]

The SS bolt will not unscrew because it has no place to go and would hit the end of the prop shaft. It is also kept snug by the lock washer and the two jam nuts.

 

[cal & pam]

I believe that the reason traditional prop zinc bolt backs out is because as the prop zinc gets eaten away it becomes sloppy against the prop nut. Normal engine operation creates zinc vibrations (oscillations) that break the thread locker bond and allow the zinc retaining screw to back out.

 

[rpmerrill]

Every season when I've hauled my boat out of the water, the zinc and the bolt were gone.
I've always thought it was plenty tight.
This year I torqued the bolt scary tight. In Early August my marina had a sale on haul and wash. The zinc was still there but fairly well chewed up. I replaced it.

Hauling in about a week.
Film at 11.

 

[rpmerrill]

Oh, one more thing.
While were on the subject, I'll pose a related question. (We may have discussed this before, but I don't think we came up with an answer.)
Why do we put zinc's on the trim tabs?
The tabs are stainless steel, as I recall.
And my tabs are thru-bolted to the transom, BUT they are not grounded on the inside.
How are these zincs contributing to protecting us without a complete circuit?
They show very little wear in comparison to my other zincs (prop and thrusters).

 

[Brian B]

I've had good luck with this product from boatzincs. Over 1100 hours of operation and haven't had any issues with the shaft bolt.
https://www.boatzincs.com/vibratite-specs.html

 

[rpmerrill]

Thanks for the recommendation.
Since we are a big group, maybe we could negotiate the price down a bit.... Ha! Nevermind.
I've put it on my winter buy list.

 

[BB marine]

I just did prop shaft anode replacement, prop removal, prop shaft inspection and cutlass bearing inspection. I do this yearly when changing all of the anodes on the boat. The prop shaft nut/anode holder designed used on the Ranger and Cutwater relies on a good fit. The cotter pin needs to be laid down properly and the nut needs to be cleaned of any corrosion or high spots to allow the anode to seat properly against the nut. If it is not fit properly it will come loose quickly after being put in service. The bolt length is important. The bolt length should be no longer than 1 or 2 threads past the threaded portion that is used to attach the anode to the nut. A thread locker will help hold the bolt in place. As the anode starts to erode away the stretch on the bolt decreases and the only holding force is the thread locker. Thread locker ( Loctite blue ) if applied when the boat is out of the water works well. It will not work in the water. The pre-applied thread locker that is used on many anode bolts helps hold the bolt in place when the bolt stretch is reduced but to work properly the contact area of the thread locker must have full bolt to nut contact. If it doesn't it can easily back out especially on a rotating shaft.

Oh, one more thing.
While were on the subject, I'll pose a related question. (We may have discussed this before, but I don't think we came up with an answer.)
Why do we put zinc's on the trim tabs?
The tabs are stainless steel, as I recall.
And my tabs are thru-bolted to the transom, BUT they are not grounded on the inside.
How are these zincs contributing to protecting us without a complete circuit?
They show very little wear in comparison to my other zincs (prop and thrusters).

The reason for the anode on the tabs is to protect the tab. The tab only. The thruster anode is the same. The thrusters are not bonded to the boats bonding system. The anode mounted on the thruster gear housing is only protecting the the thruster.


The anodes on the thruster housings are aluminum alloy. Aluminum alloy anodes are now recommended to be used in brackish and salt water applications and many of the reviews are better service life from the Aluminum alloy anode compared to the zinc anode. If you are having short service life with the zinc anode try the Aluminum Alloy to see if it gives a longer service life. If both anode materials seem to give short service life it would be a good idea to check for stray currents. An easy test, Remove a bonding wire from a thru hull place a digital amp meter between the bonding wire and the thru hull is there current passing thru? 1 milliamp or more may be a problem. Do this with shore power plug un-plugged and then check with shore power plugged in. There are many more complex testing methods but this is a easy one to perform. There is a reason why the anodes are eroding away. Boat or the environment the boat is in.

 

[baz]

The SS bolt will not unscrew because it has no place to go and would hit the end of the prop shaft. It is also kept snug by the lock washer and the two jam nuts.

Cal: Can you make a drawing of your SS bolt and the washers & lock nuts with and without the prop anode installed and post it here. I'm intrigued with your solution. Thanks... 🙂

 

[baz]

Oh, one more thing.
While were on the subject, I'll pose a related question. (We may have discussed this before, but I don't think we came up with an answer.)
Why do we put zinc's on the trim tabs?
The tabs are stainless steel, as I recall.
And my tabs are thru-bolted to the transom, BUT they are not grounded on the inside.
How are these zincs contributing to protecting us without a complete circuit?
They show very little wear in comparison to my other zincs (prop and thrusters).

The trim tab installation document indicate the tabs should not be bonded. This is why RT does not bond them.

 

[rpmerrill]

If the tabs are stainless, I wouldn't think they would need a whole lot of zinc protection?
Could they be protecting the hydraulic cylinder and rod?

In an unplanned twist, in prepping for the summer of '17, the guy at the boatyard painted my trim tabs. The old zincs were still in place, so when the paint dried, I replaced them with new zincs. (after brushing the zinc location to clean it up and make good contact. The zincs showed very little wear after the '17 season but I think I replaced them anyway. Same thing this year and that is when it occurred to me "what are they protecting?" And I discovered that the tabs weren't bonded.

Now I'm wondering, would it be an interesting (or meaningful) experiment to only pit a zinc on one tab and let the other tab run wild?

What could go wrong?
Sorry to hijack this topic. I still want to hear about prop zincs.

 

[Red Raven]

I stand corrected regarding air drying regular blue Locktite before installation. (Thanks John! 😀 ) It is incorrect. I found this from Locktite on another forum.
...

From: richard.e.avery@us.henkel.com [mailto:richard.e.avery@us.henkel.com]
Sent: Monday, March 05, 2012 7:16 AM
Subject: RE: Henkel Inquiry - Case #: 00083412 [ ref:_00D301RJ1._50080IRF10:ref ]


If I am understanding you correctly, then this will not work. Loctite 243 will not cure unless it is between two pieces of metal and restricted of air, hence the name anaerobic. It will remain a liquid if you coat the bolt and just let it sit in open air. If you need a threadlocker that can be applied underwater, you will need to use Loctite 248 Quickstix or Loctite 249 Quicktape.

Regards,

Rick Avery
Technical Engineering Representative
Henkel Corporation | AG Industrial Products
One Henkel Way
Rocky Hill, CT 06067
United States
Home - Henkel North America

...

Here is a link to Locktite 249 Quicktape which could be wrapped on the bolt threads prior to a diver installing the anode.I am liking Cal’s solution and will be looking into that as well this year for sure.

Regarding the anodes on the trim tabs I also was curious why they are needed. Without dissimilar metals in contact under the water and no bonding there should be no galvanic action. In fact, adding the anodes actually creates a galvanic cell where there was none. I asked the factory about this once and the answer came back that they follow the trim tab manufactures recommendation. I suspect the tabs would be fine without anodes but they are cheap and why take the risk? Perhaps imperfections in the SS can result in galvanic potentials? Perhaps crevice corrosion could also be the issue but I don’t know how anodes would help that.