Re: [Amel Yacht Owners] Re: Propshaft wearing ring


karkauai
 

Hi Craig.
Your description is correct, and I believe all you say about electrical potential.  The only things that are different this time from previously are the SS WOB, and the two new chargers I added about a year prior to discovering the prop shaft damage.  About two years prior to the last haul out, I changed to a MaxProp and put on their prop zinc.  It has always worn out faster than the rudder zincs.I have to believe that I will find the problem with the installation of the chargers, but will wait until I'm back on the water to check for current leaks.
I am going to add an isolator to the AC circuit after I figure out what happened.
Kent
SM243
KRISTY 

Y'all will be the first to know.


On Sep 26, 2014, at 7:44 AM, sangaris@... [amelyachtowners] <amelyachtowners@...> wrote:

 

Kent, 


If I recall correctly you had replaced the original Amel bronze "wearing out bearing" (WOB) with a stainless steel one you had fabricated, correct?  That is, you did not use an SKF "Speedi-Sleeve" over the bronze.
(Perhaps based on some of my old posts reporting the SKF engineer's input.)

If that's right it seems implausible there was electrolysis between the shaft and the WOB.  That's because, first, your new WOB was the same metal as the shaft (perhaps a different grade, but virtually the same on the electrolysis scale). Second, the WOB is electrically connected to the shaft with the retaining grub screws and therefore is at the same electrical potential.  

And, for that matter, had you used the Speedi-sleeves, the electrolysis you describe would be similarly implausible.

We'd all really like to know the exact cause of the failure, of course. You say it was under the WOB on the water side of the "O" ring, correct?  Was there anything else fitted to the shaft like "spurs" or a zinc that might enter into the equation? 

Quite the mystery.

Craig 
SN#68 - Sangaris 

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