Re: [Amel Yacht Owners] Re: Prop Shaft Electrolysis

Olivier Beaute

Good afternoon Kent,

I guess your mechanic, after a few months, will remember what he did to undo the transmission.
-secure the new lower unit onto the ballast with a new rubber sleeve, cover the bolt with black silicone filler
-the engine alignment with the upper unit must be checked
-depending on their condition/running hours, it may be good to take the opportunity for replacing the steel frame rubber mounts
-connect the C-drive box to the engine steel frame, check that the steel frame is connected to the zincs (in fact check the resistance between rudder zincs and the propeller, it should be around zero ohm).

Once the C-drive is installed and running, make sure there is no power of any kind on it, as it is originally.
 If there is a leak, it must be found and neutralized...

Bon courage.


On Thursday, January 29, 2015 8:58 PM, "Kent Robertson karkauai@... [amelyachtowners]" wrote:

Thanks, Gary.  I'll pass this along to Mike.  Makes sense to me.

I will be assisting/observing the refitting of the CDrive and Yanmar in February.  I'll post pics and a description of the process when it's all in and I've done a sea trial to make sure it's water tight.

Olivier, do you have any words of wisdom about either of these topics?

Thanks and Merci,

From: amelliahona
To: amelyachtowners@...
Sent: Thursday, January 29, 2015 2:47 PM
Subject: Re: [Amel Yacht Owners] Re: Prop Shaft Electrolysis

Hi Kent:

I have never seen a diagram of the "bonding" system. (yellow/green wires to sacrificial anodes).

As to your other question, as to why the bonding system isn't tied to the battery -ve (negative) post.  I can postulate this theory.   

The bonding system is a protective system designed to carry any stray current/leak current and any galvanically induced current to the sacrificial electrodes.  Amel wanted the DC circuits to be isolated from protective system as those circuits have current flowing thru them any time a DC circuit is in use.  Those circuits should stand on their own, ideally isolated from the bonding circuit and not having leakage current as the electrical componentry normally is "insulated" from that part of the appliance that is in contact with seawater.  In this way the protective circuit only comes into play when there is leakage current from a DC device (due to a fault) or if there is a galvanically induced current from two dissimilar metals (thru hulls etc) and the anodes. .  Remember the case or fitting of any metal object in contact with sea water is tied to the bonding system.  The alternator isn't in contact with sea water.  Its electrical componentry should stand on it's own and in the Amel strategy  the electrical componentry should be isolated electrically from the engine.   If you tie the bonding system and the DC battery negative together you put the protective circuit "on line" with all DC circuits all the time.  Additionally you now provide a parallel pathway for EMF in the seawater (perhaps from a nearby boat with an electrical fault)  to push current via the bonding system, into the DC system where it seeks ground at the battery (electrically we say sinks to ground at -ve).  The DC negative should NOT be connected to the bonding system.  The DC circuits and the bonding circuits should be separate circuits.

Again, not sure I clarified or muddied the waters.  If muddied, let me know and I will try again.

If you get a minute, I for one would be interested in how the C-drive mounts and penetrates the hull etc.  (new topic of course).

All the best, 

Gary Silver
s/v Liahona   

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