Bonding Circuit

Electrical and electronic topics for small boats
Spc337
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Joined: Thu Aug 10, 2017 4:44 am

Bonding Circuit

Postby Spc337 » Sat Sep 22, 2018 7:04 pm

[Thread moved to SMALL BOAT ELECTRICAL for discussion.]

In my Outrage 22, the bonding circuit connects to a bolt in the stern splash well. On the outboard side of the hull the head of the bolt was painted over when the bottom was epoxy coated. I'm guessing that is bad and probably the reason my metal tank failed prematurely.

How should the bonding circuit make contact with the water?
Boston Whaler 1979 V-22 Outrage

jimh
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Re: Bonding Circuit

Postby jimh » Sun Sep 23, 2018 7:23 am

The purpose of the bonding circuit is to tie all the elements of the fuel system together so that there cannot be any voltage difference between them, and then tie that circuit to the sea to establish the potential of the circuit. And outboard engine boat's 12-Volt power system negative circuit is also usually in contact with the sea via the chassis and metal components of the outboard engine.

Usually in older Boston Whaler boats the bonding circuit was connected at the transom to a dedicated electrode, located below the water line on the starboard side of the transom. The electrode was typically made of bronze and was about 2-inch-diameter. The bonding circuit wire was a 10-AWG conductor with insulation color green or yellow. The narrative above describing the connection to the sea of the bonding circuit as passing through the transom on a bolt and terminating in just "the head of a bolt" sounds unusual. As I recall, usually the bonding conductor [through] the top of the transom, down the outboard face of the transom, and is terminated in the dedicated electrode by attachment to the mounting screw of the electrode. [More details about the path of the bonding conductor at the transom to the electrode given below.--jimh]

Insulating the bonding conductor from the water by painting the bonding conductor will inhibit the bonding conductor from making electrical contact with the water.

Galvanic corrosion occurs when different metals, such as aluminum and steel, are both immersed in an electrolyte such as saltwater or even a poor electrolyte such as freshwater, and there is an electrical circuit between the two metals. When this occurs, the least noble of the metals will tend to become the anode and will begin to be eroded away by galvanic corrosion.

Spc337
Posts: 95
Joined: Thu Aug 10, 2017 4:44 am

Re: Bonding Circuit

Postby Spc337 » Sun Sep 23, 2018 10:11 am

Mine definitely is not routed like that. It is attached to what I’m describing as a bolt in the splash well and on the exterior all I can see is the head of a bolt that has been painted.

Do you have a photo of yours so I can see how this should be installed?
Boston Whaler 1979 V-22 Outrage

jimh
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Re: Bonding Circuit

Postby jimh » Sun Sep 23, 2018 11:06 am

I do not have an OUTRAGE 22 boat. I have a REVENGE 22 Whaler Drive. The bonding electrode is difficult to photograph on my boat because it is entirely hidden by the Whaler Drive.

I will emend my earlier description of the routing of the bonding conductor. After checking some images of the transom of several classic era boats, the bonding conductor may be routed through the transom, well above the static waterline and perhaps about four-inches below the top of the transom, then passed down the transom to the dedicated bonding conductor. There is a hole drilled through the transom, usually on the starboard side, again about four-inches below the top of the transom. A clamshell vent is used as a cover for the hole. The bonding conductor rises from the electrical rigging laying in the splashwell, goes under the clamshell vent, turns and passes through the transom, exits on the outboard end, is again covered by a clamshell vent, and is carried downward to the electrode. The electrode is mounted several inches below the normal static waterline of the hull. Because the electrode is located in a portion of the hull that will always be immersed in seawater, when applying anti-fouling paint, the electrode must not be painted. The insulation color of this 10-AWG conductor is typically green or perhaps yellow.

Note that Boston Whaler stopped using a dedicated electrode for the bonding system at some point in time, and began to bond the fuel system components together and then to the battery negative circuit, which was also bonded to the engine chassis and all the engine electrodes. I have not researched the exact production epoch when use of a dedicated bonding electrode was halted. There is a dedicated bonding circuit electrode on my 1990 boat.

From some previously published images on CONTINUOUSWAVE:

Image
On the OUTRAGE 18 hull the bonding circuit conductor is seen exiting the transom on starboard under a clam shell vent, then carried down the transom to the dedicated bonding circuit electrode, using a 10-AWG conductor with green insulation.

Image
On this OUTRAGE hull the bonding circuit conductor and electrode are also attached to a trim tab that has been added to the transom by the owner.

Image
This view shows the bonding circuit conductor exiting the transom on the outboard face and running down the transom on the left side of the photograph. The owner of this OUTRAGE 22 has also added another conductor, perhaps a cable to a SONAR transducer, to the path of the bonding conductor.

Image
This OUTRAGE transom picture shows the OEM bonding electrode, the conductor path, and the through-transom hole location.

I hope this further explanation and archived photographs from the CONTINUOUSWAVE website will give you a clearer understanding of how the bonding conductor circuit and the dedicated bonding electrode were installed by Boston Whaler on their hulls in the 1980's and 1990's.

jimh
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Re: Bonding Circuit

Postby jimh » Sun Sep 23, 2018 12:01 pm

Spc337 wrote:In my Outrage 22, the bonding circuit connects to a bolt in the stern splash well...


I don't have any experience with the bonding circuit being connected to a bolt in the splashwell. It is very strange electrical practice to use a mechanical fastener to carry the bonding current. Usually mechanical fasteners are only used to connect two electrical connectors. The fiberglass hull of the boat is not an electrical conductor. I presume that "bolt" means a machine screw that passes through the entire transom and exits on the other side.

In my experience, Boston Whaler would use a continuous length of 10-AWG wire with green insulation to carry the bonding circuit from one component of the circuit to another. Boston Whaler would not employ the very unusual and rather suspect method of using a mechanical fastener or machine screw or bolt of sufficient length to pass through the rather thick transom to carry this circuit through the transom.

Interrupting the bonding circuit to make a copper-to-steel-to-copper transition in the circuit adds more dissimilar metals in contact with each other, increasing the instances for galvanic corrosion to occur.

Spc337
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Joined: Thu Aug 10, 2017 4:44 am

Re: Bonding Circuit

Postby Spc337 » Sun Sep 23, 2018 3:56 pm

That all makes sense to me. Here are pictures of how my boat is currently setup.

He is a birdseye view of my splash well. It shows the Green Bond wire emerging from the starboard rigging tunnel through a clam shell (in the splashwell) attaching to a bolt (Machine Screw).

https://www.dropbox.com/s/7j5fj2zfyeslivr/BondingSplashWell.jpg?dl=0

Here is the connection to the Machine Screw

https://www.dropbox.com/s/z2z6f4qnufadkca/BondingConnection.jpg?dl=0

Here is the Exterior what looks like a slotted machine screw head albeit painted.

https://www.dropbox.com/s/fozu5br5jd8bmvk/BondingExterior.jpg?dl=0


I have read that the primary purpose of the Bonding wire is to manage static electricity between the filler on the gunwale and the tank and other metal components. The boat is technically grounded via the outboard engine which stands to reason why Whaler not couples the bonding wire to the Engine Ground.

I did find a company that makes a sintered ground button so I could always put that back on the boat but I'm leaning towards routing the Bond Wire to the engine.

Any thoughts on if my existing setup is OEM designed or altered by a prior owner?
Boston Whaler 1979 V-22 Outrage

jimh
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Re: Bonding Circuit

Postby jimh » Sun Sep 23, 2018 4:56 pm

Spc337 wrote:...Any thoughts on if my existing setup is OEM designed or altered by a prior owner?


The manner of routing the bonding circuit as shown does not look like an original installation by Boston Whaler. The several images I included above show the OEM installation of the bonding conductor on the transom of several Boston Whaler boats, and as can be seen by comparing those installations to yours, there is no resemblance. On that basis I infer that the installation on your boat was likely not the original installation from Boston Whaler.

Purpose of the bonding system

Spc337 wrote:I have read that the primary purpose of the Bonding wire is to manage static electricity between the filler on the gunwale and the tank and other metal components.


The several metal components of the fuel system are usually connected by rubber hoses, which are electrical insulators. Bonding all the metal components together gets them all at the same electrical potential.

When the metal fuel nozzle of the fuel pump is brought into contact with the boat's metal fuel filler, they should both be at ground potential. By bonding the boat system to an electrode in seawater, the boat system should be at ground potential.

I have read that the flow of an insulating liquid in a pipe can create an electrical charge. This is called "flow electrification." For this reason it is a common practice in fuel systems to have an electrical bond connecting all elements of the fuel system to ground.

Grounding of the hull of a fiberglass boat

Spc337 wrote:The boat is technically grounded via the outboard engine...

The "boat" in the case of a fiberglass boat is not a good electrical conductor, so the boat is not very well "grounded." But the boat 12-Volt electrical system negative circuit is usually bonded to the engine chassis. The engine has exposed electrodes in the seawater. This brings the boat 12-Volt negative circuit to "ground" or "sea" potential.

Spc337 wrote:...which stands to reason why Boston Whaler [does] not couple the bonding wire to the engine ground.


I believe that Boston Whaler DOES connect the bonding circuit to the battery negative and thus to the engine chassis in their new designs. I don't have good insight on why Boston Whaler initially kept the fuel system bonding circuit separate from the outboard engine chassis and battery negative circuit. I cannot offer any speculation about that.

jimh
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Re: Bonding Circuit

Postby jimh » Sun Sep 23, 2018 5:51 pm

For more advice on how to wire a boat for grounding of the fuel system, I suggest following the advice from the American Boat and Yacht Council Recommendations, Section E-01, Bonding of Direct Current Systems. If you don't have a copy of that document you can get a copy from the federal regulations of the United States of America at

https://law.resource.org/pub/us/cfr/ibr/001/abyc.E-01.1973.pdf

An excerpt is quoted below:

b. Items to be Bonded...Fuel tanks, fuel-fill deck fittings, and electrically operated fuel pumps and valve