Topics

WOB Corrosion

karkauai
 

Hi All,

I’m hauled out for bottom paint and servicing the Amel-supplied WOB and bow thruster seals.  It has been 4.3 years as I have had Island 44 on the bottom, and it lasts that long.  No water ingress and no oil loss.”, so I haven’t done the service until now.  Please see the pic of the WOB.  It is crumbling apart as if it were damaged by corrosion/electrolysis.  The hull potential has been perfect at -980mv every time I’ve checked it, and the rudder zincs have lasted almost a year with normal erosion.  I have used prop zincs on it since I had the prop shaft electrolysis a few years ago.  They have disappeared after a few months, mostly because they erode at the bolt hole edges and fall off, rather than completely erode away.

It’s going to be a bitch to get out, but bigger question is why did it corrode?  Any thoughts?  

Thanks in advance,
Kent
SM 243
Kristy

eric freedman
 

Hi Kent,

Wow,

That looks like a delicate job. Good luck with the work.

 

Looking at the picture again, had to tried to put a screwdriver or small chisel in the place where the set screw was and try to rotate the bearing, If you can get it to rotate. Possibly you can get some purchase on the lip of the bearing and pry it out. If I see the photo correctly, a pair of channel lock pliers might allow rotation and removal.

 

If that doesn’t work and  you have a flex shaft attachment for a dremel tool that would make the work a lot easier. As a jeweler that is the way I would VERY carefully grind out the remains of the bearing.

Another possibility is to drill and tap it in a few places and try  to pull it out with the screws installed in the tapped holes. Use brass screws I case they break off.

 

 

If you cover the bolts on the prop shaft zincs with varnish or nail polish, the area around the screws last a lot longer.

Fair Winds

Eric

Amel Super Maramu #376

 

 

From: main@AmelYachtOwners.groups.io [mailto:main@AmelYachtOwners.groups.io] On Behalf Of karkauai via Groups.Io
Sent: Saturday, March 28, 2020 3:32 PM
To: main@AmelYachtOwners.groups.io
Subject: [AmelYachtOwners] WOB Corrosion

 

Hi All,

I’m hauled out for bottom paint and servicing the Amel-supplied WOB and bow thruster seals.  It has been 4.3 years as I have had Island 44 on the bottom, and it lasts that long.  No water ingress and no oil loss.”, so I haven’t done the service until now.  Please see the pic of the WOB.  It is crumbling apart as if it were damaged by corrosion/electrolysis.  The hull potential has been perfect at -980mv every time I’ve checked it, and the rudder zincs have lasted almost a year with normal erosion.  I have used prop zincs on it since I had the prop shaft electrolysis a few years ago.  They have disappeared after a few months, mostly because they erode at the bolt hole edges and fall off, rather than completely erode away.

It’s going to be a bitch to get out, but bigger question is why did it corrode?  Any thoughts?  

Thanks in advance,
Kent
SM 243
Kristy

Danny and Yvonne SIMMS
 

Hi Kent, looks ugly. When your prop shaft zinks fell off did you replacen immediately. Also, the fact they just coroded around the stainless bolts could sugest limited contact with the prop. I have used cone prop zincs in the past and they corroded all over, certainly faster around the bolts. However for some years I have used shaft zincs betwen the prop and the c drive housing(i dont have line cutters) They have corroded relatively evenly.

Regards

Danny

SM 299

Ocean Pearl 

On 29 March 2020 at 08:32 "karkauai via Groups.Io" <karkauai@...> wrote:

Hi All,

I’m hauled out for bottom paint and servicing the Amel-supplied WOB and bow thruster seals.  It has been 4.3 years as I have had Island 44 on the bottom, and it lasts that long.  No water ingress and no oil loss.”, so I haven’t done the service until now.  Please see the pic of the WOB.  It is crumbling apart as if it were damaged by corrosion/electrolysis.  The hull potential has been perfect at -980mv every time I’ve checked it, and the rudder zincs have lasted almost a year with normal erosion.  I have used prop zincs on it since I had the prop shaft electrolysis a few years ago.  They have disappeared after a few months, mostly because they erode at the bolt hole edges and fall off, rather than completely erode away.

It’s going to be a bitch to get out, but bigger question is why did it corrode?  Any thoughts?  

Thanks in advance,
Kent
SM 243
Kristy

Paul Dowd and Sharon Brown
 

I think Kent may be referring to the prop zinc, not the prop shaft. I have one on my autoprop attached with three plastic bolts, and as Kent says, it always corrodes around the three bolts and can then fall off well before its useful life. I would also like to hear a solution to this.

 

Cheers,

Paul

S/Y Ya Fohi - Amel 54 #98 - Grenada

 

From: main@AmelYachtOwners.groups.io <main@AmelYachtOwners.groups.io> On Behalf Of Danny and Yvonne SIMMS
Sent: 29 March 2020 03:23
To: main@AmelYachtOwners.groups.io
Subject: Re: [AmelYachtOwners] WOB Corrosion

 

Hi Kent, looks ugly. When your prop shaft zinks fell off did you replacen immediately. Also, the fact they just coroded around the stainless bolts could sugest limited contact with the prop. I have used cone prop zincs in the past and they corroded all over, certainly faster around the bolts. However for some years I have used shaft zincs betwen the prop and the c drive housing(i dont have line cutters) They have corroded relatively evenly.

Regards

Danny

SM 299

Ocean Pearl 

On 29 March 2020 at 08:32 "karkauai via Groups.Io" <karkauai@...> wrote:

Hi All,

I’m hauled out for bottom paint and servicing the Amel-supplied WOB and bow thruster seals.  It has been 4.3 years as I have had Island 44 on the bottom, and it lasts that long.  No water ingress and no oil loss.”, so I haven’t done the service until now.  Please see the pic of the WOB.  It is crumbling apart as if it were damaged by corrosion/electrolysis.  The hull potential has been perfect at -980mv every time I’ve checked it, and the rudder zincs have lasted almost a year with normal erosion.  I have used prop zincs on it since I had the prop shaft electrolysis a few years ago.  They have disappeared after a few months, mostly because they erode at the bolt hole edges and fall off, rather than completely erode away.

It’s going to be a bitch to get out, but bigger question is why did it corrode?  Any thoughts?  

Thanks in advance,
Kent
SM 243
Kristy


--
Cheers
Paul
Ya Fohi - Amel 54 #98

Gary Wells
 

Hi Kent,

Boy, I sure don't know why it would go all zombie like that really.
Nonetheless, a few days' soaking with PB Blaster or (preferably) AeroKroil penetrant is a start.
There's a hex jet set screw holding that bushing in place too, if you get it unscrewed about halfway and exposes you can use it for leverage to try and pry the bushing free.  

Best!

Gary W.
SM 209, Adagio
Georgia,USA  

karkauai
 


Thanks for your replies.
Eric, I am able to turn it on the shaft with rotational  pressure using a screw driver, but I can’t get any purchase on the WOB, as it crumbles when any aftward pressure is applied. I may have to grind it out but will need to get a flexible shaft for my Dremel.  

Danny, I didn’t replace the prop zincs about a month ago when it disappeared, as I knew I was going to haul out and was going on the assumption that I really didn’t need it anyway.

Paul, as Eric said, if you varnish or paint with enamel (fingernail polish works, too) around the holes, they last twice as long.  You said you had plastic bolts holding your prop zinc on.  It should have three hex head stainless steel bolts which would help make contact with the prop.

Gary, the set screws are gone, their holes were so brittle that with  just a little pressure they crumbled.

I will check continuity between the prop shaft and zincs.  If I find no continuity, that would explain the problem.  If there is good continuity, does anyone have an explanation why the rudder zincs are wearing normally but I have this problem with the WOB?


Kent Robertson
S/V Kristy
SM 243

On Mar 28, 2020, at 4:30 PM, eric freedman <kimberlite@...> wrote:



Hi Kent,

Wow,

That looks like a delicate job. Good luck with the work.

 

Looking at the picture again, had to tried to put a screwdriver or small chisel in the place where the set screw was and try to rotate the bearing, If you can get it to rotate. Possibly you can get some purchase on the lip of the bearing and pry it out. If I see the photo correctly, a pair of channel lock pliers might allow rotation and removal.

 

If that doesn’t work and  you have a flex shaft attachment for a dremel tool that would make the work a lot easier. As a jeweler that is the way I would VERY carefully grind out the remains of the bearing.

Another possibility is to drill and tap it in a few places and try  to pull it out with the screws installed in the tapped holes. Use brass screws I case they break off.

 

 

If you cover the bolts on the prop shaft zincs with varnish or nail polish, the area around the screws last a lot longer.

Fair Winds

Eric

Amel Super Maramu #376

 

 

From: main@AmelYachtOwners.groups.io [mailto:main@AmelYachtOwners.groups.io] On Behalf Of karkauai via Groups.Io
Sent: Saturday, March 28, 2020 3:32 PM
To: main@AmelYachtOwners.groups.io
Subject: [AmelYachtOwners] WOB Corrosion

 

Hi All,

I’m hauled out for bottom paint and servicing the Amel-supplied WOB and bow thruster seals.  It has been 4.3 years as I have had Island 44 on the bottom, and it lasts that long.  No water ingress and no oil loss.”, so I haven’t done the service until now.  Please see the pic of the WOB.  It is crumbling apart as if it were damaged by corrosion/electrolysis.  The hull potential has been perfect at -980mv every time I’ve checked it, and the rudder zincs have lasted almost a year with normal erosion.  I have used prop zincs on it since I had the prop shaft electrolysis a few years ago.  They have disappeared after a few months, mostly because they erode at the bolt hole edges and fall off, rather than completely erode away.

It’s going to be a bitch to get out, but bigger question is why did it corrode?  Any thoughts?  

Thanks in advance,
Kent
SM 243
Kristy

<image001.jpg>

 

Kent,

You ask for, "an explanation why the rudder zincs are wearing normally but I have this problem with the WOB?

The possible answer is: If the C-Drive is not connected to the bonding system, the rudder zincs will dissolve normally because of all of the other things connected, while the prop zinc dissolves, protecting the C-drive and propeller.


CW Bill Rouse Amel Owners Yacht School
Address: 720 Winnie, Galveston Island, Texas 77550 
View My Training Calendar
cloudHQPowered by
cloudHQ


On Sun, Mar 29, 2020 at 8:17 AM karkauai via Groups.Io <karkauai=yahoo.com@groups.io> wrote:

Thanks for your replies.
Eric, I am able to turn it on the shaft with rotational  pressure using a screw driver, but I can’t get any purchase on the WOB, as it crumbles when any aftward pressure is applied. I may have to grind it out but will need to get a flexible shaft for my Dremel.  

Danny, I didn’t replace the prop zincs about a month ago when it disappeared, as I knew I was going to haul out and was going on the assumption that I really didn’t need it anyway.

Paul, as Eric said, if you varnish or paint with enamel (fingernail polish works, too) around the holes, they last twice as long.  You said you had plastic bolts holding your prop zinc on.  It should have three hex head stainless steel bolts which would help make contact with the prop.

Gary, the set screws are gone, their holes were so brittle that with  just a little pressure they crumbled.

I will check continuity between the prop shaft and zincs.  If I find no continuity, that would explain the problem.  If there is good continuity, does anyone have an explanation why the rudder zincs are wearing normally but I have this problem with the WOB?


Kent Robertson
S/V Kristy
SM 243

On Mar 28, 2020, at 4:30 PM, eric freedman <kimberlite@...> wrote:



Hi Kent,

Wow,

That looks like a delicate job. Good luck with the work.

 

Looking at the picture again, had to tried to put a screwdriver or small chisel in the place where the set screw was and try to rotate the bearing, If you can get it to rotate. Possibly you can get some purchase on the lip of the bearing and pry it out. If I see the photo correctly, a pair of channel lock pliers might allow rotation and removal.

 

If that doesn’t work and  you have a flex shaft attachment for a dremel tool that would make the work a lot easier. As a jeweler that is the way I would VERY carefully grind out the remains of the bearing.

Another possibility is to drill and tap it in a few places and try  to pull it out with the screws installed in the tapped holes. Use brass screws I case they break off.

 

 

If you cover the bolts on the prop shaft zincs with varnish or nail polish, the area around the screws last a lot longer.

Fair Winds

Eric

Amel Super Maramu #376

 

 

From: main@AmelYachtOwners.groups.io [mailto:main@AmelYachtOwners.groups.io] On Behalf Of karkauai via Groups.Io
Sent: Saturday, March 28, 2020 3:32 PM
To: main@AmelYachtOwners.groups.io
Subject: [AmelYachtOwners] WOB Corrosion

 

Hi All,

I’m hauled out for bottom paint and servicing the Amel-supplied WOB and bow thruster seals.  It has been 4.3 years as I have had Island 44 on the bottom, and it lasts that long.  No water ingress and no oil loss.”, so I haven’t done the service until now.  Please see the pic of the WOB.  It is crumbling apart as if it were damaged by corrosion/electrolysis.  The hull potential has been perfect at -980mv every time I’ve checked it, and the rudder zincs have lasted almost a year with normal erosion.  I have used prop zincs on it since I had the prop shaft electrolysis a few years ago.  They have disappeared after a few months, mostly because they erode at the bolt hole edges and fall off, rather than completely erode away.

It’s going to be a bitch to get out, but bigger question is why did it corrode?  Any thoughts?  

Thanks in advance,
Kent
SM 243
Kristy

<image001.jpg>

karkauai
 

Of course you are right, Bill.  I was going to check continuity between the prop shaft and the rudder zincs.  That wouldn’t have anything to do with the bilge strap.

Kent Robertson
S/V Kristy
SM 243

On Mar 29, 2020, at 9:23 AM, CW Bill Rouse <brouse@...> wrote:


Kent,

You ask for, "an explanation why the rudder zincs are wearing normally but I have this problem with the WOB?

The possible answer is: If the C-Drive is not connected to the bonding system, the rudder zincs will dissolve normally because of all of the other things connected, while the prop zinc dissolves, protecting the C-drive and propeller.


CW Bill Rouse Amel Owners Yacht School
Address: 720 Winnie, Galveston Island, Texas 77550 
View My Training Calendar
cloudHQPowered by
cloudHQ


On Sun, Mar 29, 2020 at 8:17 AM karkauai via Groups.Io <karkauai=yahoo.com@groups.io> wrote:

Thanks for your replies.
Eric, I am able to turn it on the shaft with rotational  pressure using a screw driver, but I can’t get any purchase on the WOB, as it crumbles when any aftward pressure is applied. I may have to grind it out but will need to get a flexible shaft for my Dremel.  

Danny, I didn’t replace the prop zincs about a month ago when it disappeared, as I knew I was going to haul out and was going on the assumption that I really didn’t need it anyway.

Paul, as Eric said, if you varnish or paint with enamel (fingernail polish works, too) around the holes, they last twice as long.  You said you had plastic bolts holding your prop zinc on.  It should have three hex head stainless steel bolts which would help make contact with the prop.

Gary, the set screws are gone, their holes were so brittle that with  just a little pressure they crumbled.

I will check continuity between the prop shaft and zincs.  If I find no continuity, that would explain the problem.  If there is good continuity, does anyone have an explanation why the rudder zincs are wearing normally but I have this problem with the WOB?


Kent Robertson
S/V Kristy
SM 243

On Mar 28, 2020, at 4:30 PM, eric freedman <kimberlite@...> wrote:



Hi Kent,

Wow,

That looks like a delicate job. Good luck with the work.

 

Looking at the picture again, had to tried to put a screwdriver or small chisel in the place where the set screw was and try to rotate the bearing, If you can get it to rotate. Possibly you can get some purchase on the lip of the bearing and pry it out. If I see the photo correctly, a pair of channel lock pliers might allow rotation and removal.

 

If that doesn’t work and  you have a flex shaft attachment for a dremel tool that would make the work a lot easier. As a jeweler that is the way I would VERY carefully grind out the remains of the bearing.

Another possibility is to drill and tap it in a few places and try  to pull it out with the screws installed in the tapped holes. Use brass screws I case they break off.

 

 

If you cover the bolts on the prop shaft zincs with varnish or nail polish, the area around the screws last a lot longer.

Fair Winds

Eric

Amel Super Maramu #376

 

 

From: main@AmelYachtOwners.groups.io [mailto:main@AmelYachtOwners.groups.io] On Behalf Of karkauai via Groups.Io
Sent: Saturday, March 28, 2020 3:32 PM
To: main@AmelYachtOwners.groups.io
Subject: [AmelYachtOwners] WOB Corrosion

 

Hi All,

I’m hauled out for bottom paint and servicing the Amel-supplied WOB and bow thruster seals.  It has been 4.3 years as I have had Island 44 on the bottom, and it lasts that long.  No water ingress and no oil loss.”, so I haven’t done the service until now.  Please see the pic of the WOB.  It is crumbling apart as if it were damaged by corrosion/electrolysis.  The hull potential has been perfect at -980mv every time I’ve checked it, and the rudder zincs have lasted almost a year with normal erosion.  I have used prop zincs on it since I had the prop shaft electrolysis a few years ago.  They have disappeared after a few months, mostly because they erode at the bolt hole edges and fall off, rather than completely erode away.

It’s going to be a bitch to get out, but bigger question is why did it corrode?  Any thoughts?  

Thanks in advance,
Kent
SM 243
Kristy

<image001.jpg>

Thomas Peacock
 

Hi Kent,

I hope you and Iris are weathering this non-meteorological storm well.

Galvanic corrosion is one of my (many) weak suits, but I’m isolated and have some time to let my imagination go nuts. 

The obvious pattern which appears is that, to my knowledge, you are the only person who has experienced galvanic corrosion of the WOB. You are also the only person who has had his C-drive melted by galvanism. I can’t help but look for a connection. I know that when you replaced the C-drive, you were ultra-fastidious. But, it is a complicated device. I would have to agree with Bill Rouse that I am worried about the C-drive not being protected by the bonding system, and that the WOB is taking the heat for now. I agree that the prop shaft needs to be tested for continuity; I would also test the innermost part of the C-drive that you can access in the engine compartment. My memory is that the C-drive has green and yellow wires attached via the engine frame, maybe also directly to the C-drive. All the wires look good? No chance there are nylon spacers anywhere in the construction?

My memory is that the zinc on the prop shaft is not really necessary, we have a plastic hub. Indeed, the zinc would always fall off in a few months. Someone of authority, not sure if it was Bill or Olivier, explained that the zinc was not necessary. Does it make a difference if you are using steel or nylon bolts to secure it (in terms of your corrosion problem)?

As an aside, I know some owners have foregone the Amel WOB (brass, I think) in favor of a stainless steel WOB. Obviously stainless is more durable to wear, but if you do have a galvanic issue, and if you had a stainless WOB, you might not have noticed anything. I guess the old Captain is right again.

Tom Peacock
SM #240 Aletes
San Juan, Puerto Rico
But I got nervous and flew back to the US

On Mar 29, 2020, at 9:17 AM, karkauai via Groups.Io <karkauai@...> wrote:


Thanks for your replies.
Eric, I am able to turn it on the shaft with rotational  pressure using a screw driver, but I can’t get any purchase on the WOB, as it crumbles when any aftward pressure is applied. I may have to grind it out but will need to get a flexible shaft for my Dremel.  

Danny, I didn’t replace the prop zincs about a month ago when it disappeared, as I knew I was going to haul out and was going on the assumption that I really didn’t need it anyway.

Paul, as Eric said, if you varnish or paint with enamel (fingernail polish works, too) around the holes, they last twice as long.  You said you had plastic bolts holding your prop zinc on.  It should have three hex head stainless steel bolts which would help make contact with the prop.

Gary, the set screws are gone, their holes were so brittle that with  just a little pressure they crumbled.

I will check continuity between the prop shaft and zincs.  If I find no continuity, that would explain the problem.  If there is good continuity, does anyone have an explanation why the rudder zincs are wearing normally but I have this problem with the WOB?


Kent Robertson
S/V Kristy
SM 243

On Mar 28, 2020, at 4:30 PM, eric freedman <kimberlite@...> wrote:



Hi Kent,

Wow,

That looks like a delicate job. Good luck with the work.

 

Looking at the picture again, had to tried to put a screwdriver or small chisel in the place where the set screw was and try to rotate the bearing, If you can get it to rotate. Possibly you can get some purchase on the lip of the bearing and pry it out. If I see the photo correctly, a pair of channel lock pliers might allow rotation and removal.

 

If that doesn’t work and  you have a flex shaft attachment for a dremel tool that would make the work a lot easier. As a jeweler that is the way I would VERY carefully grind out the remains of the bearing.

Another possibility is to drill and tap it in a few places and try  to pull it out with the screws installed in the tapped holes. Use brass screws I case they break off.

 

 

If you cover the bolts on the prop shaft zincs with varnish or nail polish, the area around the screws last a lot longer.

Fair Winds

Eric

Amel Super Maramu #376

 

 

From: main@AmelYachtOwners.groups.io [mailto:main@AmelYachtOwners.groups.io] On Behalf Of karkauai via Groups.Io
Sent: Saturday, March 28, 2020 3:32 PM
To: main@AmelYachtOwners.groups.io
Subject: [AmelYachtOwners] WOB Corrosion

 

Hi All,

I’m hauled out for bottom paint and servicing the Amel-supplied WOB and bow thruster seals.  It has been 4.3 years as I have had Island 44 on the bottom, and it lasts that long.  No water ingress and no oil loss.”, so I haven’t done the service until now.  Please see the pic of the WOB.  It is crumbling apart as if it were damaged by corrosion/electrolysis.  The hull potential has been perfect at -980mv every time I’ve checked it, and the rudder zincs have lasted almost a year with normal erosion.  I have used prop zincs on it since I had the prop shaft electrolysis a few years ago.  They have disappeared after a few months, mostly because they erode at the bolt hole edges and fall off, rather than completely erode away.

It’s going to be a bitch to get out, but bigger question is why did it corrode?  Any thoughts?  

Thanks in advance,
Kent
SM 243
Kristy

<image001.jpg>



Mark & Debbie Mueller
 

Hi Kent, 

 

I do like the Dremel idea; it will allow you to section the WOB and remove it like a dentist removes a wisdom tooth. 

 

I wanted to let you know that every time I have ordered prop shaft zincs they have come with the plastic screws.  The zinc has exhibited “normal” wear but has never fallen off.  The Autoprop website has a video showing the rebuild of an H5 and references removing the plastic screws when disassembling the prop.  I believe metal screws provide a preferential contact area on the mounting tabs enhancing the destruction of the tabs whereas the plastic screws spread out the contact area to the body of the zinc – just a SWAG.

 

Good luck with your project.


--
Mark Mueller
Brass Ring  A54

karkauai
 

Thanks, Mark.  Interesting to know.  I have a MaxProp Classic.  They sell stainless steel hex bolts for the zinc.
Anyone have suggestions for something I can put between the zinc and aft side of the prop to improve contact?

I was able to remove the bad WOB by drilling two holes and using screws to pull it out.  It came out with just a little coaxing.

See pic.  The galvanic damage extended about half way through the WOB.

I tested continuity between the prop shaft and bonding system and found NO LOAD!!!
Further investigation showed bad connections between the CDrive and engine bed.  After cleaning those up, still NO LOAD. Cable was bad, too, inside the connectors.
I've now confirmed no resistance between the prop shaft and the rudder zincs.

If this had been worse, I could have had catastrophic failure of the WOB, and who knows what kind of other damage...I got lucky this time.

Soooo, bottom line for me is that while hull potential is a good measure of overall bonding efficacy, we must REGULARLY measure continuity at ALL metals exposed to sea water to confirm that they are protected.  It goes on my quarterly maintenance list today.

Kent
SV Kristy
SM 243

On Mar 29, 2020 1:17 PM, Mark & Debbie Mueller <brass.ring@...> wrote:

Hi Kent, 

 

I do like the Dremel idea; it will allow you to section the WOB and remove it like a dentist removes a wisdom tooth. 

 

I wanted to let you know that every time I have ordered prop shaft zincs they have come with the plastic screws.  The zinc has exhibited “normal” wear but has never fallen off.  The Autoprop website has a video showing the rebuild of an H5 and references removing the plastic screws when disassembling the prop.  I believe metal screws provide a preferential contact area on the mounting tabs enhancing the destruction of the tabs whereas the plastic screws spread out the contact area to the body of the zinc – just a SWAG.

 

Good luck with your project.


--
Mark Mueller
Brass Ring  A54

karkauai
 

Oops forgot to attach pic:


On Mar 29, 2020 1:53 PM, "karkauai via Groups.Io" <karkauai@...> wrote:
Thanks, Mark.  Interesting to know.  I have a MaxProp Classic.  They sell stainless steel hex bolts for the zinc.
Anyone have suggestions for something I can put between the zinc and aft side of the prop to improve contact?

I was able to remove the bad WOB by drilling two holes and using screws to pull it out.  It came out with just a little coaxing.

See pic.  The galvanic damage extended about half way through the WOB.

I tested continuity between the prop shaft and bonding system and found NO LOAD!!!
Further investigation showed bad connections between the CDrive and engine bed.  After cleaning those up, still NO LOAD. Cable was bad, too, inside the connectors.
I've now confirmed no resistance between the prop shaft and the rudder zincs.

If this had been worse, I could have had catastrophic failure of the WOB, and who knows what kind of other damage...I got lucky this time.

Soooo, bottom line for me is that while hull potential is a good measure of overall bonding efficacy, we must REGULARLY measure continuity at ALL metals exposed to sea water to confirm that they are protected.  It goes on my quarterly maintenance list today.

Kent
SV Kristy
SM 243

On Mar 29, 2020 1:17 PM, Mark & Debbie Mueller <brass.ring@...> wrote:

Hi Kent, 

 

I do like the Dremel idea; it will allow you to section the WOB and remove it like a dentist removes a wisdom tooth. 

 

I wanted to let you know that every time I have ordered prop shaft zincs they have come with the plastic screws.  The zinc has exhibited “normal” wear but has never fallen off.  The Autoprop website has a video showing the rebuild of an H5 and references removing the plastic screws when disassembling the prop.  I believe metal screws provide a preferential contact area on the mounting tabs enhancing the destruction of the tabs whereas the plastic screws spread out the contact area to the body of the zinc – just a SWAG.

 

Good luck with your project.


--
Mark Mueller
Brass Ring  A54


eric freedman
 

Kent,

In that case I would drill and tap it in 3 or 4 places.

You will need a small wrench to turn the tap.

Use brass screws in case they  break—or possibly drill it and insert a few  eazy outs to pull the bearing out . It seems like you will have to drill deeply to get the bearing . Worse case it is rotten all the way through and then you will have to grind it out.

 

Was there any brass in the drain oil?

 

Fair Winds

Eric

Amel Super Maramu #376

 

 

 

From: main@AmelYachtOwners.groups.io [mailto:main@AmelYachtOwners.groups.io] On Behalf Of karkauai via Groups.Io
Sent: Sunday, March 29, 2020 9:18 AM
To: main@amelyachtowners.groups.io
Subject: Re: [AmelYachtOwners] WOB Corrosion

 



Thanks for your replies.

Eric, I am able to turn it on the shaft with rotational  pressure using a screw driver, but I can’t get any purchase on the WOB, as it crumbles when any aftward pressure is applied. I may have to grind it out but will need to get a flexible shaft for my Dremel.  

 

Danny, I didn’t replace the prop zincs about a month ago when it disappeared, as I knew I was going to haul out and was going on the assumption that I really didn’t need it anyway.

 

Paul, as Eric said, if you varnish or paint with enamel (fingernail polish works, too) around the holes, they last twice as long.  You said you had plastic bolts holding your prop zinc on.  It should have three hex head stainless steel bolts which would help make contact with the prop.

 

Gary, the set screws are gone, their holes were so brittle that with  just a little pressure they crumbled.

 

I will check continuity between the prop shaft and zincs.  If I find no continuity, that would explain the problem.  If there is good continuity, does anyone have an explanation why the rudder zincs are wearing normally but I have this problem with the WOB?

 

Kent Robertson

S/V Kristy

SM 243



On Mar 28, 2020, at 4:30 PM, eric freedman <kimberlite@...> wrote:



Hi Kent,

Wow,

That looks like a delicate job. Good luck with the work.

 

Looking at the picture again, had to tried to put a screwdriver or small chisel in the place where the set screw was and try to rotate the bearing, If you can get it to rotate. Possibly you can get some purchase on the lip of the bearing and pry it out. If I see the photo correctly, a pair of channel lock pliers might allow rotation and removal.

 

If that doesn’t work and  you have a flex shaft attachment for a dremel tool that would make the work a lot easier. As a jeweler that is the way I would VERY carefully grind out the remains of the bearing.

Another possibility is to drill and tap it in a few places and try  to pull it out with the screws installed in the tapped holes. Use brass screws I case they break off.

 

 

If you cover the bolts on the prop shaft zincs with varnish or nail polish, the area around the screws last a lot longer.

Fair Winds

Eric

Amel Super Maramu #376

 

 

From: main@AmelYachtOwners.groups.io [mailto:main@AmelYachtOwners.groups.io] On Behalf Of karkauai via Groups.Io
Sent: Saturday, March 28, 2020 3:32 PM
To: main@AmelYachtOwners.groups.io
Subject: [AmelYachtOwners] WOB Corrosion

 

Hi All,

I’m hauled out for bottom paint and servicing the Amel-supplied WOB and bow thruster seals.  It has been 4.3 years as I have had Island 44 on the bottom, and it lasts that long.  No water ingress and no oil loss.”, so I haven’t done the service until now.  Please see the pic of the WOB.  It is crumbling apart as if it were damaged by corrosion/electrolysis.  The hull potential has been perfect at -980mv every time I’ve checked it, and the rudder zincs have lasted almost a year with normal erosion.  I have used prop zincs on it since I had the prop shaft electrolysis a few years ago.  They have disappeared after a few months, mostly because they erode at the bolt hole edges and fall off, rather than completely erode away.

It’s going to be a bitch to get out, but bigger question is why did it corrode?  Any thoughts?  

Thanks in advance,
Kent
SM 243
Kristy

<image001.jpg>

Gary Silver
 

On Sun, Mar 29, 2020 at 11:55 AM, karkauai wrote:
bottom line for me is that while hull potential is a good measure of overall bonding efficacy, we must REGULARLY measure continuity at ALL metals exposed to sea water to confirm that they are protected.  It goes on my quarterly maintenance list today.

Hi Kent:  What a great find and a great discussion along with Joel's post.  Sooooo valuable.  Thanks for sharing.  Glad you got that WOB (wearing out bearing) out.  It is still a bit of a mystery to me as to why only that corroded.  The color (salmon like) looks like de-zincification.  I am only speculating but, since brass is copper and zinc, the zinc in the brass was the least noble element in that vicinity (i.e.the prop, c-drive shaft etc.) Everything must have all been more noble metals, so with no continuity of the C-drive to the normal sacrificial anodes (on the rudder), the WOB became the sacrificial anode for your C-drive.  I guess it only corroded where it was in contact with sea water and hence the lack of corrosion "inside" the lip seals etc. 

Again, thanks for you invaluable reminder about preventative diagnostics on our bonding system. 

Gary S. Silver
s/v Liahona    (Puerto Del Rey Marina, in-accesible due to Puerto Rico's COVID-19 quarantine)
SM 2000 # 335

Danny and Yvonne SIMMS
 

Hi Gary, I think you have put your finger on it. That erosion of the exterior of the WOB is something I have never seen and your reasoning that the least noble metal eroded sounds right. Brass is an alloy of copper and zinc. However bronze alloys come in a variety of compositions, I believe some with zinc and some not.(but I am no expert on alloys) I always thought the WOB was a bronze, if so it would seem likely that Kents did indeed contain zinc. Whatever I am sure you have picked the cause. Once again we see good reason to stay with the Amel original. If the bronze WOB had been replaced with a stainless what may have happened?

Regards

Danny

SM 299 Ocean Pearl

On 31 March 2020 at 06:33 "Gary Silver via Groups.Io" <garysilver@...> wrote:

On Sun, Mar 29, 2020 at 11:55 AM, karkauai wrote:
bottom line for me is that while hull potential is a good measure of overall bonding efficacy, we must REGULARLY measure continuity at ALL metals exposed to sea water to confirm that they are protected.  It goes on my quarterly maintenance list today.

Hi Kent:  What a great find and a great discussion along with Joel's post.  Sooooo valuable.  Thanks for sharing.  Glad you got that WOB (wearing out bearing) out.  It is still a bit of a mystery to me as to why only that corroded.  The color (salmon like) looks like de-zincification.  I am only speculating but, since brass is copper and zinc, the zinc in the brass was the least noble element in that vicinity (i.e.the prop, c-drive shaft etc.) Everything must have all been more noble metals, so with no continuity of the C-drive to the normal sacrificial anodes (on the rudder), the WOB became the sacrificial anode for your C-drive.  I guess it only corroded where it was in contact with sea water and hence the lack of corrosion "inside" the lip seals etc. 

Again, thanks for you invaluable reminder about preventative diagnostics on our bonding system. 

Gary S. Silver
s/v Liahona    (Puerto Del Rey Marina, in-accesible due to Puerto Rico's COVID-19 quarantine)
SM 2000 # 335

Danny and Yvonne SIMMS
 

Hi again Gary and Kent, further to my last. I do depart from Amel advice regarding zincs. Because the c drive, the shaft and the propeller are so critical I always have a shaft zinc between the prop and the c drive. Yes the Amel bonding system makes this unnecessary, but only if all the connections are always perfect and in my long experience it is very difficult on a boat to be certain that all connections are always perfect. This is my backup defence. I know it can be argued that this means I am "over zincing" but I prefer that risk to the other. I have the plastic cone on the prop.

Kind regards

Danny

SM 299

Ocean Pearl 

On 31 March 2020 at 06:33 "Gary Silver via Groups.Io" <garysilver@...> wrote:

On Sun, Mar 29, 2020 at 11:55 AM, karkauai wrote:
bottom line for me is that while hull potential is a good measure of overall bonding efficacy, we must REGULARLY measure continuity at ALL metals exposed to sea water to confirm that they are protected.  It goes on my quarterly maintenance list today.

Hi Kent:  What a great find and a great discussion along with Joel's post.  Sooooo valuable.  Thanks for sharing.  Glad you got that WOB (wearing out bearing) out.  It is still a bit of a mystery to me as to why only that corroded.  The color (salmon like) looks like de-zincification.  I am only speculating but, since brass is copper and zinc, the zinc in the brass was the least noble element in that vicinity (i.e.the prop, c-drive shaft etc.) Everything must have all been more noble metals, so with no continuity of the C-drive to the normal sacrificial anodes (on the rudder), the WOB became the sacrificial anode for your C-drive.  I guess it only corroded where it was in contact with sea water and hence the lack of corrosion "inside" the lip seals etc. 

Again, thanks for you invaluable reminder about preventative diagnostics on our bonding system. 

Gary S. Silver
s/v Liahona    (Puerto Del Rey Marina, in-accesible due to Puerto Rico's COVID-19 quarantine)
SM 2000 # 335

karkauai
 

Gary and Danny,
I am certain that you are right about the WOB acting as the sacrificial anode.
If this had gone on any longer, might have had catastrophic failure of the WOB.  What damage would have occurred if that had happened?  I think that the shaft zinc might be a good solution. Serving the same purpose as the prop zinc.  With added protection I think the stainless WOB would be OK. Thoughts?
Kent
Kristy
SM 243

On Mar 30, 2020 1:33 PM, "Gary Silver via Groups.Io" <garysilver@...> wrote:
On Sun, Mar 29, 2020 at 11:55 AM, karkauai wrote:
bottom line for me is that while hull potential is a good measure of overall bonding efficacy, we must REGULARLY measure continuity at ALL metals exposed to sea water to confirm that they are protected.  It goes on my quarterly maintenance list today.

Hi Kent:  What a great find and a great discussion along with Joel's post.  Sooooo valuable.  Thanks for sharing.  Glad you got that WOB (wearing out bearing) out.  It is still a bit of a mystery to me as to why only that corroded.  The color (salmon like) looks like de-zincification.  I am only speculating but, since brass is copper and zinc, the zinc in the brass was the least noble element in that vicinity (i.e.the prop, c-drive shaft etc.) Everything must have all been more noble metals, so with no continuity of the C-drive to the normal sacrificial anodes (on the rudder), the WOB became the sacrificial anode for your C-drive.  I guess it only corroded where it was in contact with sea water and hence the lack of corrosion "inside" the lip seals etc. 

Again, thanks for you invaluable reminder about preventative diagnostics on our bonding system. 

Gary S. Silver
s/v Liahona    (Puerto Del Rey Marina, in-accesible due to Puerto Rico's COVID-19 quarantine)
SM 2000 # 335


Danny and Yvonne SIMMS
 

Thanks Kent. I would stay with the bronze WOB. It saved you this time. Without it that corosion would have happened somewhere else.

Regards

Danny

SM 299

Ocean Pearl

On 31 March 2020 at 10:34 "karkauai via Groups.Io" <karkauai@...> wrote:

Gary and Danny,
I am certain that you are right about the WOB acting as the sacrificial anode.
If this had gone on any longer, might have had catastrophic failure of the WOB.  What damage would have occurred if that had happened?  I think that the shaft zinc might be a good solution. Serving the same purpose as the prop zinc.  With added protection I think the stainless WOB would be OK. Thoughts?
Kent
Kristy
SM 243

On Mar 30, 2020 1:33 PM, "Gary Silver via Groups.Io" <garysilver@...> wrote:
On Sun, Mar 29, 2020 at 11:55 AM, karkauai wrote:
bottom line for me is that while hull potential is a good measure of overall bonding efficacy, we must REGULARLY measure continuity at ALL metals exposed to sea water to confirm that they are protected.  It goes on my quarterly maintenance list today.

Hi Kent:  What a great find and a great discussion along with Joel's post.  Sooooo valuable.  Thanks for sharing.  Glad you got that WOB (wearing out bearing) out.  It is still a bit of a mystery to me as to why only that corroded.  The color (salmon like) looks like de-zincification.  I am only speculating but, since brass is copper and zinc, the zinc in the brass was the least noble element in that vicinity (i.e.the prop, c-drive shaft etc.) Everything must have all been more noble metals, so with no continuity of the C-drive to the normal sacrificial anodes (on the rudder), the WOB became the sacrificial anode for your C-drive.  I guess it only corroded where it was in contact with sea water and hence the lack of corrosion "inside" the lip seals etc. 

Again, thanks for you invaluable reminder about preventative diagnostics on our bonding system. 

Gary S. Silver
s/v Liahona    (Puerto Del Rey Marina, in-accesible due to Puerto Rico's COVID-19 quarantine)
SM 2000 # 335