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

Eric Freedman

Hi Kent,

Would you mind summarizing the steps you have taken to measure your ”problem”

and your findings?


What do you perceive is wrong? Is it the fact that there is voltage between the bonding and the 24 volt battery negative.


As an additional thought, there is a battery shunt behind the outboard side of the battery bank “tub”.

The negative for the entire battery bank is connected to one side of the shunt an the DC for the boat is connected to the other side.

Did you inspect it to see if there is some type of short between it and the bonding.


My second thought is possibly the battery monitor has some connection to the bonding somewhere.

On the shunt there are some small wires to operate the battery monitor. Did you try  disconnecting all of them,  let them hang and try to see if you still have a connection between the bonding and the DC negative?

Don’t forget to mark them as to where they go.  Leave the big negative cables connected to the shunt otherwise you will have no DC on the boat.


You did check the bonding between  the DC negative and the case of the battery charger ?

Also the inverter.  Did you isolate these items?


Really grabbing at straws here.

However you have peaked my interest and I can’t wait to get back to Kimberlite and see what I find.

Fair Winds


Kimberlite Amel Super Maramu #376



Did you open and remove the fuse behind the battery switches?


From: amelyachtowners@... [mailto:amelyachtowners@...]
Sent: Saturday, December 19, 2015 12:14 AM
To: amelyachtowners@...
Subject: Re: [Amel Yacht Owners] Re: Prop Shaft Electrolysis



Hi Eric,

Yes, there are two cables and one small wire on the (+) and (-) poles on the battery side of the 24v switch.

*Battery cable

*24v charger cable

*"Permanent " wire for the 

24->12v converter that powers the radio and retains its memory.


I have the same issue whether the charger and Permanent are connected or not.


I had an electrician come to the boat today from Savannah who does mostly galvanic/electrolytic surveys for a living. He spent several hours on the boat with me and checked everything thoroughly.  While he couldn't identify the source of the 24vDC between the battery (+) and the bonding system, he was convinced that it has nothing to do with my zincs disappearing too quickly.  There is no change in hull potential when this is present (battery switch on) versus absent(battery switch off).

Although the 24vDC does light a 2.5 watt bulb, there is infinite resistance when checking the battery (-) to bonding system.


He says most 53' boats with all the systems we have use 2-3 times as much zinc as we do.


While I don't like the fact that I don't have a clear explanation, I don't know of anything else to do but keep a close watch on my zincs and hull potential.


I'll keep posting as I learn more or find new issues that shed light on this.


Merry Christmas!




On Dec 18, 2015, at 7:20 PM, sailormon kimberlite@... [amelyachtowners] <amelyachtowners@...> wrote:



Possibly I do not remember correctly, but I thought there was an inline fuse just hanging from some a wire

behind the battery switches. I think that has to do with memory of the cd changer/radio. Just a memory from 13 years ago at the Amel introductory class. I wish I was on board to check it for you.

Fair Winds


Kimberlite Amel Super Maramu #376



From: amelyachtowners@... [mailto:amelyachtowners@...]
Sent: Sunday, December 06, 2015 4:12 PM
To: amelyachtowners@...
Subject: Re: [Amel Yacht Owners] Re: Prop Shaft Electrolysis



Thanks, John.  That's what I've decided to do with my 220AC system.


Now chasing down a connection between 24v DC (+) main cable (that goes from the main battery switch to the lug on the foreword bulkhead in the engine room...disconnected from all other cables at the lug) and the bonding system.  When checking resistance, it is a solid (no resistance) connection that carries enough amps to light a test bulb when the main battery switch is on and all 24v breakers are off (including the ones in the engine room, passageway, and foreword port locker).  When the switch is off it has no voltage, but still shows a no resistance connection.  If I disconnect battery + cable in the battery compartment, the connection disappears.  The negative side shows no connection or voltage with the switch either on or off.


The only 24v equipment that is connected to the battery side of the main switch is the Charles 60 Amp charger, and the "Permanent " 24->12V Sailor transformer under the Nav station.


Does any of this suggest to anyone where the connection is?


I'm in the Jacksonville FL area, does anyone know of a good...make that Great...marine electrician nearby?


Thanks again everyone for your patience and help.




Fernandina Beach FL

On Dec 5, 2015, at 7:22 PM, jjjk12s@... [amelyachtowners] <amelyachtowners@...> wrote:


Is this a case of PREVIOUSLY the risk was so small, and the disandvatages significant, that the AC generator ground - neutral connection was not made, whereas nowadays, with readily available galvanic isolators and a more litiginous society the small risk overcomes the disadvantages and it should be connected. So it would be sensible to modify older designs that may have been correct at the time where circumstances have moved on. Amels have always evolved so modifying an older Amel to mirror a newer Amel's systems seems totally in order and not messing with Cpt Henry's concepts.



Maramu #91 1981

Join to automatically receive all group messages.