Re: Earth bonding and watermaker

ngtnewington Newington

Thanks Bill,

I agree that the really important connection between the C drive and the rudder zincs needs to be 100% and the for example salt water pump for the anchor wash is less of a worry.

When I go back to Amelia in April, she is ashore, I will make up an extension to my multimeter and check for continuity between the zincs on the rudder and various bits and bobs around the boat, before launching. I have no corrosion on the keel or prop or anywhere and I want to keep it that way!!!!


On 14 Mar 2019, at 17:59, CW Bill Rouse <brouse@...> wrote:


I think that most of your questions were directed to me and I already stated that I am not an electrical engineer. Maybe some should be directed to SAV at Amel.

I will answer from my experience. 
  • The connections between the yellow/green bonding wire and devices will get corroded even if the wire is not soldered.
  • The resistance between the propellor and the anode should be zero or almost zero
  • I believe that the connections should be clean and free of paint and corrosion. 
  • I believe that you should check on each 2-year haulout the resistance between the rudder anodes and the propellor. This check will verify, engine, transmission, and C-Drive.
  • I think the Amel Bonding System is more than adequate. Keep in mind that there are many builders that bond nothing! Amel bonds most water connections, even when it is saltwater that is the most common culprit.
  • Some of the connections are more important than others, but at least one owner experienced significant C-Drive damage and the propellor is vulnerable if the bonding connection to the C-Drive fails
  • If you suspect something is going on, connect a wire to the rudder post quadrant and test resistance between it and the C-Drive. You are looking for good continuity and almost zero resistance.
  • Once you have verified engine, transmission & C-Drive, checking resistance between the C-Drive and various other bonding connections should ensure that the various other bonding connections are adequate, if the resistance is near zero.
  • On SN, SM, & 54, visually inspect the bonding strap inside the grey water bilge to ensure that the copper strap is OK beginning at the stainless steel nut at the bottom up to the yellow/green wire(s) junction at the top. You will have to pump 100% of the water out using a wet vac or similar. The most common place for a break is within about 3" of the stainless steel nut and even 1/2" of water will hide a break. If it is broken, replace it because this protects your cast iron ballast from electrolysis. Use 1/8" X 2" copper bar...don't use stainless steel for many reasons.

I hope that this helps.


Bill Rouse
720 Winnie St.
Galveston, Texas 77550

On Thu, Mar 14, 2019 at 11:58 AM ngtnewington Newington via Groups.Io <> wrote:
Hi Bill,

I meant to say well done to all those involved with setting up the new owners site. Thanks.

Good bonding connections????

How good can we expect the connections on the bonding circuits to be? I note that on my boat and from pictures in the owners manuals that the yellow/green wires that are used for the bonding circuit are not tinned (I think) and very often are connected to say a metal object with a hose clamp and some of the plastic insulation removed from the wire, linking one fitting to the next in a ring.  These connections will invariably become oxidised and green. Given the very low voltages, the connection will be poor. I have made an effort to improve the connections where practical, by changing some hose clamps for new and cleaning up the surfaces, but I wonder how far to go. I was always taught that one should use a dedicated insulated lug with a soldered connector and a copper bolted on lug for all bonding connections, and to avoid clamping uninsulated wire with a hose clamp to, say, a through hull fitting or a saltwater manifold, for example.

Do you think the original connection system is adequate? How important are these connections? Do you think it a good idea to measure the resistance between the Zincs on the rudder and various connected fittings around the boat? If so what might be an acceptable reading?

Kind regards


S/Y Amelia hull 019  Aml 54
On 14 Mar 2019, at 15:06, CW Bill Rouse <brouse@...> wrote:


Of course I do not know exactly the cause of the corrosion, but it may be saltwater caused corrosion and was not caused by a missing or poor bonding connection. 

I am not an electrical engineer. Let me attempt to give you a Bill Rouse explanation and answer to your question. Be sure to read all of the Electrical Warnings in your Amel 54 User and Owners manual (You may want to ask SAV at Amel, afterall, that is what they are there for):

Bonding Connections on your Amel 54 were designed to electrically connect devices in contact with water to the anodes on the rudder. There is micro voltage in this pathway and the least amount of corrosion between the bonding wire and the device will cause issues similar to no bonding connection. The metal where the yellow/green wire connects should be free of paint and very clean. The same thing for the bare end of the wire.

EARTH Connections on your Amel 54 are designed to protect you from electrical shock. These connections should cause either the Main breaker to open or the device breaker to open when a 220VAC load line connects to the yellow/green EARTH. An example would be your 220VAC dessalator pump motor has a EARTH connection. If possibly saltwater was spilled on the pump creating a connection between the 220VAC load line and EARTH, breakers will open cutting OFF the 220VAC load line to the electric motor. If in this example if the EARTH connection to the motor was broken, the possibility of electric shock will exist when you touch the motor or anything connected to the motor.

EARTH and Bonding are separate systems, but sometimes EARTH meets Bonding on your Amel 54. A good example of this is the original Calpeda A/C pump. It is connected to Bonding at the output pipe. The 220VAC EARTH is connected to the metal case inside the wiring box. And, of course, the metal case is connected to the output pipe, thus EARTH and Bonding are connected. I believe that the same thing is true on your Dessalator Duo.

I hope this explanation helps. 


Bill Rouse
720 Winnie St.
Galveston, Texas 77550

On Thu, Mar 14, 2019 at 7:50 AM Arno Luijten <arno.luijten@...> wrote:
Hi All,

I'm wondering about a thing after removing my Duo watermaker. I noticed quite some galvanic corrosion despite the fact that the green/yellow bonding wire was attached at several points to the watermaker.
I was actually just in time taking the thing apart as I'm still able to salvage all the important bits.
From traces I could see I'm guessing one of the endcaps on the pump has been leaking also given the amount of salt build-up at the chassis and pump-base.

What I'm wondering about is the bonding sytem. Is it also connected to the shore power earth lead? From earlier conversations I vaguely remember it was not connected.  If not then why is the earth connection of the 230 Volt pump connected to the mains earth?

Any advise appreciated.

Arno Luijten
SV Luna,

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