Re: [Amel Yacht Owners] Bonding


Pat, if the hull potential is different from the drive than from the engine and everything else, it isn't connected well to the rest of the bonding system.  Normally you would see a better reading at the engine than at the drive.  If you don't have a prop zinc, I can't explain the findings.  If you have two problems, a bad connection at the rudder, and a bad connection at the drive, they would read differently.  If you have a prop zinc it could be protecting the drive but the rudder zincs not protecting the rest of the boat.
Get in the engine room with your multitester and look for resistance between all bonded parts and the strap, including the rudder post.  There should be essentially no resistance between all bonded equipment.
To check the zinc connection to the rudder, you have to haul the boat out and run a wire from the rudder post to the zincs and check resistance.

Does that make sense?  If not, please chime in!


On Sep 22, 2016, at 11:58 AM, Patrick Mcaneny sailw32@... [amelyachtowners] <amelyachtowners@...> wrote:


Kristy, Why do you think the drive connection has failed , if it shows Like -1000mv , I may have left off the - in my email , is that why? I guess the engine can be bonded to the zincs without being grounded ? I have no prop zinc , and don't understand how the strap and the Cdrive are so different in their reading.
Thanks ,

-----Original Message-----
From: Kent Robertson karkauai@... [amelyachtowners] <amelyachtowners@...>
To: amelyachtowners <amelyachtowners@...>
Sent: Thu, Sep 22, 2016 9:13 am
Subject: Re: [Amel Yacht Owners] Bonding

Hi Pat.  It sounds like your drive connection to the bonding system has failed.  Do you have a prop zinc?  On Kristy the connection to the bonding system is at one of the bolts on the housing at the top of the vertical drive shaft.  Around -1000mv hull potential is correct for your boat.  Your 804 (I assume really -804mv) reading indicates under protection of the whole system, so I would first check the connections between the strap and the rudder.  I hope you'll find something there, as that would be the simplest thing to fix.  If they are all OK, you'll need to check connections of the zincs to the rudder.  Only way I know to do that is haul the boat out and check continuity from the zinc to the rudder post.  I guess you could remove the zincs and wire brush the bolts and bottle brush the bolt holes with a SS or Brass brush if you can find one.

Let us know what you find.


On Sep 22, 2016, at 8:37 AM, sailw32@... [amelyachtowners] <amelyachtowners@...> wrote:

How is the Cdrive & engine protected , if it not connected to the bonding system. With the silver anode the electrician had a reading over 1000 mv at the C-Drive, and at the strap 804. With the battery connection off, everything off it was 804 , with everything on ,still 804 . I suppose the 804 could be explain by poor zinc/bolt contact and the test being conducted in fresh water. If the engine is not grounded / bonded , how is it protected?
Thanks ,
Pat SM 123

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