Transom Electrode Purpose

[bassemir]

My 1991 Outrage 17 has a disk on the transom with a broken wire. The wire looks like a copper stranded wire. I tried to trace this wire's path but was unsuccessful. I see the wire going up the [rigging] tunnel towards the console, but I do not see it come out under the console.

Fig. 1. Very small image showing the bronze anode on the transom of a Boston Whaler OUTRAGE boat.

transom.jpg (8.39 KiB) Viewed 6713 times

Q1: what is the purpose of the disk on the transom on my 1991 OUTRAGE?

Q2: is the purpose of the disk important?

ASIDE
I am a new Boston Whaler owner.

[Phil T]

[The disk on the transom of the 1991 OUTRAGE 17] is part of the grounding system for the fuel tank.

There is a wire with green insulation that goes from the fuel fill firring to the fuel tank and then a second wire that leads overboard to an [electrode] that is under the waterline.

You can replace [the broken connection to electrode], or you can reroute the green wire to the negative terminal of the battery.

There should be a little slack in the wire. A ring terminal should be added to the wire end.

[bassemir]

PHIL T--thank you.

[jimh]

Q1: what is the purpose of the disk on the transom on my 1991 OUTRAGE.

The purpose the metal disk (or disc) is to create an electrical connection to the sea. The disk is made of bronze. It is not intended to be a sacrificial anode. The disk is an electrode. The reason for using bronze is precisely to PREVENT erosion of the metal disk by galvanic corrosion. To this disk a copper wire is connected. A number of other metal components of the boat are also electrically connected to the disk.

Q2: is the purpose of the disk important?

The purpose of the disk [or disc] is to establish a voltage potential that would typically be referred to as "ground" but since the boat is at sea, it is the potential of the sea. The disk works better in saltwater than in freshwater because saltwater is a better electrical conductor than very pure freshwater. The disk becomes part of an electrical circuit when the green wire is connected to the disc.

THE PURPOSE OF THE WIRE CONNECTED TO THE DISK

The wire connected to the disk becomes part of a circuit that connects to the metal fuel tank, the metal fuel inlet filler fitting, and the metal vent fitting. The purpose of this electrical circuit is to maintain all the elements of the fuel system that are conductive at the exact same voltage. This is VERY IMPORTANT. This circuit is the fuel tank bonding circuit

WHY THE FUEL TANK AND OTHER METAL COMPONENTS OF THE FUEL SYSTEM ARE BONDED TOGETHER

Gasoline fuel is an extremely good insulator of electrical current. When gasoline fuel is flowing from the fuel dispensing nozzle into the fuel filler hoses and into the tank, it is possible for an electrical charge (a "static" charge) to be created from the motion because the fuel itself is not conductive in any way. This is called the TRIBOELECTRIC EFFECT. In order to prevent a build up of electrical charge, the metal components are joined together by very low resistance wire. This is why a 10-AWG wire is used. The wire has green insulation in order to identify it as a ground or bonding circuit.

WHY THE CIRCUIT IS ISOLATED
This circuit is never connected to any other electrical wiring in the boat. It remains isolated, and is only connected to the transom electrode. There should never be any current flowing on this circuit related to current flow from or to the boat battery. The only current flowing will be the discharge of any static electricity before it can build up any voltage difference between the conductive parts of the fuel system.

YOUR REMEDY TO REPAIR THE DEFECT YOU HAVE DISCOVERED
I recommend you reestablish the connection of the wire with green insulation to the bronze anode on the transom.

I see the wire going up the [rigging] tunnel towards the console, but I do not see it come out under the console.

That is normal. The green wire does not connect to any other electrical circuit in the boat. It only connects to the metal components of the fuel system: the filler inlet fitting, the vent fitting, the metal tank fuel tank, and the bronze disk on the transom.

SOME HISTORY
For many years all Boston Whaler boats that had below deck internal aluminum fuel tanks and associated fuel filler fitting and tank vent fittings were electrically connected together using a rather large 10-AWG copper wire with green insulation (or in some later years with yellow insulation). This practice continued into the 1990's, as evidenced by the appearance of the bronze anode on a 1991 model year boat. At some point--I do not know the exact epoch--Boston Whaler stopped installing the bronze transom electrode. After than, the fuel bonding circuit was connected to the battery negative because the battery negative would be connected to the outboard engines chassis, and the outboard engine chassis would be in contact with the sea via the exposed electrodes on the underwater portions of the outboard engine gear case and mounting bracket, which are, indeed, sacrificial anodes, but in the case of the fuel bonding circuit are just a substitute for the bronze electrode previously used.

There may have been some change in the recommendations of the American Boat and Yacht Council regarding the acceptable methods for bonding the fuel system metal components together and how that circuit would be connected to the sea which might have changed Boston Whaler's method for providing the fuel bonding circuit connection to the sea. I really have not researched this. Or, they might have decided to save money and eliminate the bronze anode and running an extra wire over the transom. I am sure that when the use of the overboard disk electrode ended, a Boston Whaler boat was still in full compliance with any USCG regulations or ABYC recommendations.

[bassemir]

Very interesting update Jim, thanks. I will connect it back up. I might see if I can get a new copper disk.

Rich

[jimh]

A copper electrode won’t work or last. Only use bronze.

[Rfich53]

In reference to this disk, my 1993 Outrage 17 has the white [conductor] from a disk [or disc on the transom presumably below the waterline and made of bronze] routed over the transom and then to the port side thru [some opening or path] where it ends with a severely corroded female spade connection. I have search under the gunwale around the fuel fill fitting for a matching male connector. No luck locating.

Q3: what was the original electrical connection for this white wire from the transom electrode on my 1993 OUTRAGE 17?

[jimh]

Q3: what was the original electrical connection for this…wire [with white insulation] from the transom electrode on my 1991 OUTRAGE 17?

Most likely the conductor with (what is now) white insulation was connected to some metal part of the fuel system. From your description it sound like it was terminated with a push-on or spade connector, so it would have been connected to a matching tab, possibly on the metal fuel tank. Typically a metal fuel tank would have a tang welded to it with the end shaped to receive an electrical conductor, and this was used for making an electrical connection to the metal tank for the bonding circuit. There really is no other logical purpose in having that bronze electrode on the transom other than for an isolated bonding system for the fuel system.

About the only other purpose might have been envisioned was to connect to the battery negative bus, but usually if there is a dedicated bonding anode that circuit would be isolated from the battery negative bus, which itself is connected to the sea by the chassis of the outboard engine.

A really long-shot guess is the electrode was installed by a prior owner and was perhaps used with some sort of active anti-galvanic corrosion system that has since been removed, but that seems very far fetched.

Also, the insulation color was probably yellow or green originally. That the wire had white insulation seems unusual to me. Perhaps the insulation color faded to white from exposure to sun and water over 34-years.

Q4: what is the wire diameter in the AWG wire size system?

Typically the wire was a rather large 10-AWG conductor.

Q5: is there any marking or identification label on the wire?

Having no marking would not be unusual as the insulation color (green or yellow) would have served to indicate the circuit.

Q6: do you have a detailed wiring diagram for the boat?

Again, in 1991 there might not be a detailed schematic diagram, as the boat electrical wiring was very simple. Boston Whaler tended to not include model-specific electrical diagrams on their smaller boats. It was only when Boston Whaler began making larger boats with much more complex electrical circuits involving both DC and AC systems that they began to provide detailed electrical wiring diagrams and marked every individual wire to aid in identification and noted the wire numbers on the the schematic diagrams.

[Rfich53]

The wire from the bronze [electrode] is definitely white. [The diameter of the insulated conductor is] similar to an antenna cable in white and there are no markings.

I just opened rear access port to [the internal fuel] tank and the fuel gauge flange that is bolted to the tank has a red positive wire and a black negative wire attached routed to center console. The same negative post on fuel gauge port has a male spade with no wire and no rust. I've read whaler revised fuel bonding eliminating bronze and bonded with green wire loop in 1991.

Again my Outrage is 1993, with the bronze bond.

I went to a whaler dealership and saw the green grounding loop on the new Boston Whaler and Parker boats.

I've been searching for the factory wiring diagram unsuccessfully. I went to the whaler home page for pdf—no luck.

[Rfich53]

Jmh, I've re read your very detailed reply Aug 14, 2023. That is another curiosity on my 1993, there is no wire from fuel filler neck to tank to complete a bonding circuit as you clearly described in your post back in 2023. There isn't a green wire to be.found any where under the console either. Now that I know about this fuel system bonding circuit, I'm concerned about a kaboom! Before now, my ignorance was bliss as the saying goes.

[jimh]

Q7: Is the fuel filler fitting on this particular boat made of metal?

Usually the bonding conductor is wound around the rubber hose and goes to the fuel tank.

Q8: Is the fuel tank metal?

[Rfich53]

Yes, the fuel filter is a metal base and a metal canister, with no place for male connector. No wires wound around any fuel lines including fill line to tank or supply line to engine.
I specifically looked for that "circuit" of wires on my lines after viewing the green wire fuel system bonding installed on new Whalers and Parker boats when I went to showroom asking same question.
I tried calling Whaler in Florida, but basically got told to look at the Whaler library of pdf. Couldn't find any info for my year.

[Rfich53]

My original owners manual contains two wiring diagrams as follows:

17 ft Montauk and Outrage
This shows nothing concerning fuel system bonding.

19 ft Outrage II
This shows grounding plate outside transom
and from that plate two conductors, one to fuel tank and one to negative bus bar.

Again my 17 Outrage has the one 1 wire from transom plate to attach to something.

The only two wires from fuel tank are a red wire and a black wire to console. No other wires.

The only thing I see on the fuel tank is an unused male spade/barb connector that is integral to where the black wire also attaches to the fuel gage sending unit on top of tank.

[jimh]

Yes, the fuel filter is a metal base and a metal canister, with no place for male connector.

I was asking about the fuel FILLER fitting. Usually they are metal so when the metal pump hose spout is placed into the fuel fill inlet there is an electrical connection made between the boat fuel system and the dispensing pump.

For example, if the boat is on a trailer and is being fueled at a highway fuel station, the boat fuel bonding circuit is tied to the ground circuit on the dispensing pump. But now, saying that, I will have to look more closely at the dispensing pump to see where their ground conductor is provided on the end of their hose.

I found this comment on a website discussing retail fuel dispensing:

Anti-Static Components

Static electricity can be a significant hazard during refueling. To counter this, gas pump nozzles are designed with anti-static components that reduce the risk of sparks. This includes the use of materials that do not easily accumulate static charge. As well as the integration of grounding mechanisms.

Cf.: https://aochenggroup.com/news/how-gas-p ... les-work/#

[Rfich53]

My apology, yes fuel filler is original metal.

I have searched under gunwale for any remnants of a male spade attached to filler and found nothing.

Once rain stops, I'm about to re-open deck access port to the fuel tank where fuel [gauge] assembly has a red and black wire terminated for the [gauge]. Black wire terminal which is attached with ring terminal also [there is] an unused male spade. I'm thinking the white 10-AWG conductor from transom bond might attach there

Looking at wire diagram for an Outrage 19, the conductor wire from transom bonds to the fuel tank. That would mean fuel tank bond would be connected to battery negative.

Thanks for your help with this.

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[Rfich53]

I will share my findings concerning my 1993 Outrage 17 fuel bonding wiring conundrum.

This 1993 OUTRAGE 17 utilized the factory-installed transom-mounted bronze disk for fuel system bonding. I've determined that the white 10-AWG conductor, that I recently found laying disconnected on the port side of the bilge, should be attached to the metal fuel filler neck from the underside of the gunwale utilizing a ring terminal connector retained between the machine screw and hex nut of the three fasteners (two others are wood screws) that secure the fuel filler neck to the gunwale.

I found the remains of the corroded ring terminal connector when I removed the nut from the bolt.

I have determined that my 1993 Outrage 17 factory-installed fuel system bonding wiring matches the Owner's Manual wiring diagram titled "Electrical Diagram 19' Outrage II". A second wiring diagram included in the same Owners Manual is titled "Electrical Diagram 17' Montauk & 17' Outrage" but doesn't show the fuel system bonding wiring at all. This is from the original Owner’s Manual provided by Boston Whaler when this 1993 Outrage 17 was purchased.

jmh--thanks for your help.

[jimh]

From your narrative I am inferring that the remaining part of what was once a ring terminal connector that broke apart and fell off the machine screw binding it to the metal fuel filler was mistaken for a male spade connector in your initial examination of the loose conductor you found in the stern area. This makes the situation clear: the bonding conductor originally had a ring terminal connector, not a male spade connector, and was connected to the fuel filler inlet fitting.

Q9: was there an indication of another conductor bonding the fuel tank?

Also, you did not remark about the fuel tank construction.

Q10: was the fuel tank a metal tank?

At some time around this epoch Boston Whaler used some molded plastic fuel tanks instead of welded aluminum tanks, but I do not have a handle on exactly when and on which models they might have tried plastic fuel tanks.

ASIDE
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