Need Shaft, Prop & Rudder Bonding Advice

[GaylesFaerie]

Not surprisingly Gayle's Faerie (2012 R27 Classic) lost her prop zinc this past season which as I've read on the forums is a pretty common event. On haul out, all that remained was the toothed washer with an itty bit of zinc on it. The allen head nut held fine with the thread lock I applied. I had painted the prop and rudder and I didn't notice any corrosion, so am counting myself lucky.

I've seen all the prop zinc remedies on Tugnuts and the fact that there are so many and they work for some and not others leads me to want to add a reliable backup for protecting the prop, rudder and shaft.

I'm thinking of adding a shaft brush and wiring it (8 AWG) directly to a transom zinc but am a bit confused by all the solutions I've seen on Tugnuts.

Shaft brush: https://www.suremarineservice.com/Elect ... SB-6B.html

Transom zinc: https://www.boatzincs.com/Vetus-8.html It weighs 2.2 lbs compared to the 1.6 lbs of the D size Prop zinc and only requires a single bolt keeping things simple.

I assume the wiring configuration above would protect the shaft and prop. But what about the rudder? Would I need to run a second wire from the transom zinc to the rudder? or would going to the bonding bus bar protect the rudder (and other underwater metals as well)?

I'd appreciate any critiques / advice. Thanks, Gary

Bonus question: does anyone know what material the stringers under the engine mounts are composed of? I would be installing a small piece of starboard on the stringer to fasten the shaft brush to and don't know if drilling into the stringer will hit only fiberglass and wood or is there metal plate along the stringer? Or is drilling not necessary and something like 4200 would suffice?

 

[tranmkp]

I had a cathodic check on my 2015 27 done and was told all the voltage readings were fine. I was also told that yes, if I hung a big zinc in the water it would really help ONLY if it had good contact with the shaft - something like a collar - but it would need to be removed when you use the boat. Planning on doing that. Will also try to bond the exhaust collar too.

 

[Red Raven]

If you connect your transom anode to the bonding buss bar then the rudder should also be protected as it is tied to the bonding system. You can also very easily add a clamshell anode to the rudder itself with a single hole. Another option to avoid drilling a hole in the boat under the water line (needed for the transom anode) is to add collar anodes to the swimstep stainless supports under the water line. The swimstep supports should already be bonded. In any case, if you add a shaft brush it should be tied to the bonding system buss.

BTW, I have found it is actually pretty easy to tighten the prop anode every several months to keep it snug with just a snorkel and an Allen wrench. The snorkel air inlet fits in the space below the swimstep and you can easily reach the prop anode without holding your breath. Keeping it snug reduces the chance it will come apart from banging around on the prop nut. At best the prop anode will still only last 6 months at our Marina in Oak Harbor, Wa. It is not difficult to change the prop anode with a snorkel, allen wrench, and thread locker tape. While you are under there you can also clean the trim tabs and pistons with scotchbrite pads! 😀

Curt

 

[GaylesFaerie]

Thanks Curt. So I'll have the transom anode connected to the shaft brush and bus bar. Interesting that you mention the swim platform struts. Mine are not bonded that I can see. The boat came to me with shaft anodes on each strut and I repeated that this past season. I painted the struts from their attachment points on the boat up above the water level under the platform (not where the anodes go tho). At the end of the season those zincs looked almost new. G

 

[Red Raven]

My boat is a 2014 so maybe they started to bond the swimstep struts in the build years between yours and mine. In any case they are easily bonded as they are bolted through the hull. You should see three bolts and nuts inside the hull for each one (except the one under the ladder which is different). Just attach green #8 marine copper stranded wire from strut to strut (on any one of the three bolts from each strut) and then to the bonding buss or nearest bonded connection.

Both the shaft brush and the transom anode can be attached to the nearest item that is already bonded if you don’t want to run them all they way back to the buss bar. Just make sure there is a good solid connection along the whole path back to the buss bar.

Curt

 

[tranmkp]

These are the readings

We found -0.854 VDC hull potential on the bonded metals.
I think we found +\-6 ma. AC current when clamping your shore power cord. Both of those readings are within acceptable limits.

 

[BB marine]

Gayle, Reading your post and the discussion after I have a few questions. Do you have any other bonded anodes on the boat now ? If you do not have a divers dream or a transom anode of some kind attached to your hull with a bonding wire now. What anode do you think is protecting the hardware under the water? The anodes that are protecting the thrusters are not bonded. The sole purpose of the thruster anodes is to protect the thruster. If the swim platform struts are not bonded the shaft anodes that are attached are only protecting the strut that it is attached to. The anodes on the trim tab planes are also stand alone the planes are not bonded so the anodes are protecting the trim tab planes.

The Prop shaft anode will be a 50/50 chance of being bonded. The quick and easy test is take a VOA meter set on lowest ohm setting and check for resistance between the shaft and a bonded thru hull fitting. If you see 1 or less at the time you check, then at that present time the prop shaft is bonded thru the transmission. There may be times that it isn't but I'm going to guess better that 50% of the time it is.

The prop shaft anode on you boat is eroded away. Why ? Because it isn't bonded ? No because it is the only anode protecting the boats underwater metal hardware.

If I was trying to resolve the issue of the prop shaft erosion I would not try to bond it. I would first try adding a bonded transom divers dream or bonding each swim platform strut and adding shaft anodes to the struts. Adding addition anodes under water will take the load off the prop shaft anode and let it do what it is intended to do protect the Prop and shaft.

This was another component of early day Ranger Tug and Cutwater builds weakness. The folks there did a good job bonding most of the hardware but failed to install a anode to protect everything. When I purchased my Cutwater new from the factory it came with NO anodes except a prop shaft anode. There were no anodes on the trim tabs, there wasn't a hull anode (divers dream) The thrusters had the factory installed anodes from side power. How is everything under water protected ? The prop shaft anode! Why does the prop shaft anode erode away so fast? Because that is not enough protection!

Before going thru the efforts of installing a ground brush to the shaft. Try to install a hull anode, Divers dream or do what Curt suggested. Ground the struts and add a shaft anode to each one. Give it a season and see what happens. I believe you will see less erosion at the prop anode.

Try using Aluminum alloy anodes. I have had good results. I installed all aluminum alloy anodes on my Cutwater and now installing them on my Mainship. Better for the environment and the seem to hold up better.

 

[Bob/Bradenton]

Gayle's: I drilled a hole in the forward/lower area of my rudder and installed a pancake zinc on it. Did the same for the trim tabs. Also installed a Galvanic Isolator. Bob/Bradenton

 

[GaylesFaerie]

Hi Brian,

Do you have any other bonded anodes on the boat now ?

No.

What anode do you think is protecting the hardware under the water?

The D size prop zinc that fits over the castle nut holding the prop on.

The anodes that are protecting the thrusters are not bonded.

Correct, they just protect the legs inside the tubes.

If the swim platform struts are not bonded the shaft anodes that are attached are only protecting the strut that it is attached to.

Correct, they just protect the four struts which are not bonded.

The anodes on the trim tab planes are also stand alone the planes are not bonded so the anodes are protecting the trim tab planes.

Correct, I installed clam shells on each plane last winter when I discovered that the stock anodes both were 100% gone including three lost ferrules designed to maintain solid contact for the bolts between the pivoting bracket at the end of the piston rod and the plane. Those lost ferrules resulted in the starboard plane being always floppy. It may explain why that piston has a leak and needs replacing.

The quick and easy test is take a VOA meter set on lowest ohm setting and check for resistance between the shaft and a bonded thru hull fitting.

I will check that. Thanks.

The prop shaft anode on you boat is eroded away. Why ? Because it isn't bonded ? No because it is the only anode protecting the boats underwater metal hardware.

I'm not so sure it was ONLY because it was protecting. Take a look at this photo of the prop.

https://share.icloud.com/photos/0d0IxKz ... 89ugryO-aA

All that is left of the anode is the toothed washer with a little bit of zinc. I assumed (maybe incorrectly) that the anode didn't have a chance to do its full job and eroded in such a way as to fall off after some time. When I hauled the boat out the season before after purchasing the boat there was a significant amount of the prop anode still in place so I assumed I fell victim to doing a poor installation or bad luck that others have experienced with this anode design. Here is a picture from the year before when boat spent most of its time in a Rhode Island bay near Tiverton, RI...

https://share.icloud.com/photos/004e6tF ... hhkqeaEaSQ

Before going thru the efforts of installing a ground brush to the shaft. Try to install a hull anode, Divers dream or do what Curt suggested. Ground the struts and add a shaft anode to each one. Give it a season and see what happens. I believe you will see less erosion at the prop anode.

Yah, I'm going to install a hull anode. I'm on the fence tho about the shaft brush. I recently cleaned the wires and bonding connection going to my stuffing box (my surveyor didn't like what he saw). After I was done I got 0.3 Ohms between the stuffing box nut and my battery negative. When I tried the shaft I got "OL" on the VOA meter, hence my desire for the shaft brush. Multiple engine / transmission parts also read below 1 Ohm. Is there something about shaft brushes in particular that concern you? I'd hate to go another season and have the D anode just work its way off again. Also the shaft brush would be accessible, is less work to install and easier to check and maintain. Trying to bond all four swim platform struts means taking the whole stern seat compartment apart including my propane tank, Big Orange filter, wood panels etc. and a repeat just to check all those bonded connections.

Try using Aluminum alloy anodes. I have had good results. I installed all aluminum alloy anodes on my Cutwater and now installing them on my Mainship. Better for the environment and the seem to hold up better.

My understanding (flawed as it may be) is that boats in salt water all the time (mine) are best served by zinc. In brackish water, Aluminum is preferred because of its enhanced reactivity where there is less salt to make the erosive and protective action work. I've also read that Aluminum passivates quicker than zinc which can render the anode useless if not cleaned on a regular basis. All supposition based on me googling. What do you think?

Thanks for contributing. This discussion is all really helpful. Gary

 

[BB marine]

Here is a few articles that googling will pull up.
https://www.cruisingworld.com/how/zinc- ... ial-anodes
https://www.absolutemarine.co.nz/image/ ... num_anodes.
https://martyranodes.com/ go to the "Support" drop down and click go to" Why Zinc-less"

Here are photos of 6 month anodes that I removed off my Cutwater. These anodes were used in Fresh water 6 weeks a couple weeks in Brackish water the rest in Florida gulf and Atlantic coast salt water (4 months). 90% of the time in marina's . ( I did have a Galvanic Isolator.)


These are Martyr Aluminum anodes
gallery2.php?g2_itemId=81355

I'm

Is there something about shaft brushes in particular that concern you? I'd hate to go another season and have the D anode just work its way off again. Also the shaft brush would be accessible, is less work to install and easier to check and maintain. Trying to bond all four swim platform struts means taking the whole stern seat compartment apart including my propane tank, Big Orange filter, wood panels etc. and a repeat just to check all those bonded connections.

There is nothing that concerns me about using shaft brushes. The Idea of the shaft brush is to make sure the shaft and prop are protected. If the only anode you have on the boat is the prop anode that may possibly be bonded 50% of the time to the rest of the boat. The shaft brush isn't going to help. If you add additional anodes that are bonded and install a shaft brush It may help preserve the prop anode. My thoughts were if you added more anodes plus switch to aluminum you may not need the shaft brushes. Just my opinion.

 

[GaylesFaerie]

Hi Brian,

Read the links except number 2 which produced "The page you requested cannot be found!". No big deal.

So if I understand correctly Aluminum is great for a mixture of waters used in a season like you describe and on the Martyr site. I'm always in salt and OK to stay with zinc for now.

My main question is this: If I add a shaft brush and a transom anode both wired into the bonding system and my prop anode bites the dust by lets say falling off, will the shaft and prop still be protected by the shaft brush? I understand that the transom anode will reduce the erosion for the prop zinc but if that zinc were to disappear, I want backup. I believe the brush will do that, no? Thanks, Gary

 

[BB marine]

I believe you are correct. Bonding brushes with an additional anode mounted on the transom will protect the underwater gear.

You are correct to the Zinc anode will work ok only in salt water. So it is ok to use it. My point about the Aluminum is it will work as good and last longer than the Zinc anode in salt water.

 

[GaylesFaerie]

I believe you are correct. Bonding brushes with an additional anode mounted on the transom will protect the underwater gear.

Great, thanks for the confirmation.

You are correct to the Zinc anode will work ok only in salt water. So it is ok to use it. My point about the Aluminum is it will work as good and last longer than the Zinc anode in salt water.

Understood, I'm just not ready to make that change yet.

Gary