Re: WOB Corrosion

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 
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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

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