Fuel System Ground Wiring on c.1986 OUTRAGE

Electrical and electronic topics for small boats
Don SSDD
Posts: 107
Joined: Fri Oct 23, 2015 6:58 am
Location: Nova Scotia

Fuel System Ground Wiring on c.1986 OUTRAGE

Postby Don SSDD » Sun May 20, 2018 1:26 pm

In replacing the fuel lines and doing some electrical [on a 1986 Boston Whaler boat] I have a question on ground wires;

I get ground from the negative side of the battery for the electrical system. What ground wires should I be seeing for the fuel tank?

There is a wire from the filler to the top of the tank where the filler hose connects.

Is there supposed to be any [wiring to] the vent hose connection area forward of the console? If yes, where does it connect?

There is a [metal welded ] tab in the stern area on top of the fuel tank where the [fuel supply to engine] hose connects and feeds fuel to the priming bulb. There is nothing connected to that tab. It looks as if there was a place there to hold a ground wire connection and it is rusted off. Should that be a ground connection?

Thanks,
Don
1986 Outrage 18 with 2001 Honda 130 HP
Former Owner 1991 Guardian 19 with 1994 Evinrude V4 140HP
Former owner 1987 Montauk with 1998 Mercury 90HP
Nova Scotia

jimh
Posts: 4687
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: Fuel System Ground Wiring on c.1986 OUTRAGE

Postby jimh » Sun May 20, 2018 1:40 pm

All metallic components of the fuel system should be connected together by a 10-AWG conductor with GREEN insulation. That conductor will typically connect to:

  • the fuel filler inlet metal fitting
  • the vent fitting
  • the fuel tank itself, often at a welded-on tab in the aft portion[*)the circular fuel withdrawal plate where the fuel pick-up fittings and hoses attach
  • a dedicated transom-mounted bronze electrode that is below the waterline

This circuit is the fuel bonding conductor circuit. Its purpose is to make certain that all metal components of the fuel system are held at the same voltage, and that voltage is the zero-voltage or ground or reference voltage. The dedicated bonding electrode immersed in the sea determines the common voltage level.

The wiring can be from each element to a common bus connection, or, more often seen, a daisy-chain from device A to B to C to D and so on. There must be no loops in the circuit, such as A to B to C and back to A.

If there is no transom mounted bronze electrode dedicated to the bonding system, the bonding system is connected ONLY at one point to the battery negative bus. There must never be a second connection anywhere between the bonding circuit and the battery negative; this is necessary to prevent any current from flowing on the bonding system circuit.

In an outboard powered boat, the battery negative will generally be bonded to the metal chassis of the outboard engine, and the outboard engine will have exposed electrodes in contact with the sea to establish the reference voltage. Those anodes are usually part of a galvanic corrosion prevention system. Make certain there is good electrical continuity--zero resistance--from the sacrificial galvanic corrosion anodes and the engine chassis and battery negative bus.

The several 10-AWG conductors with GREEN insulation are usually fitted with a RING terminal connector at each end, and the ring terminal is fasted with a machine screw to the metal component of the fuel system.

The presence of a corroded electrical connection point on the fuel tank is worrisome. The lack of strong bonding conductors may have permitted some galvanic corrosion of the aluminum fuel tank if it was floating without an electrical bond to ground.

Don SSDD
Posts: 107
Joined: Fri Oct 23, 2015 6:58 am
Location: Nova Scotia

Re: Fuel System Ground Wiring on c.1986 OUTRAGE

Postby Don SSDD » Sun May 20, 2018 1:57 pm

I've not seen a transom mounted bronze electrode.

The wire at the filler neck is heavy gauge green, so any other wire connected originally by Whaler would have been the same wire as that?

What did the wire from the vent area connect with?

The metal tab I mention at the stern area where the fuel line connects in on the cover, not on the tank itself, should there be a connection on the tank as well as on the cover? Does one of these connect to the negative battery terminal? Or where do they connect?

Thanks Jim.
1986 Outrage 18 with 2001 Honda 130 HP
Former Owner 1991 Guardian 19 with 1994 Evinrude V4 140HP
Former owner 1987 Montauk with 1998 Mercury 90HP
Nova Scotia

jimh
Posts: 4687
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: Fuel System Ground Wiring on c.1986 OUTRAGE

Postby jimh » Sun May 20, 2018 2:02 pm

All conductors in the OEM bonding circuit were the same: 10-AWG conductors with GREEN insulation, as I earlier described.

The fuel withdrawal circular plate has its own bonding point, as it will often be insulated by a rubber seal from the tank itself. I will add that to the list above.

I added more description to my remarks above about the path of the wiring.

To understand why GREEN is used for the BONDING circuit, see the marine wire insulation color code table at

http://continuouswave.com/whaler/reference/wireColorCode.html#BW

Don SSDD
Posts: 107
Joined: Fri Oct 23, 2015 6:58 am
Location: Nova Scotia

Re: Fuel System Ground Wiring on c.1986 OUTRAGE

Postby Don SSDD » Mon May 21, 2018 4:31 am

[Should I run] a 10-AWG green wire from the filler (A) to the vent (B) to the fuel tank itself at a welded-on tab in the aft portion (C), to the circular fuel withdrawal plate where the fuel pick-up fittings and hoses attach (D), and last to the negative battery terminal (E)?

On the machine screw, I should not use a stainless screw due to galvanic reaction with the aluminum tank?

Thanks for the help.
1986 Outrage 18 with 2001 Honda 130 HP
Former Owner 1991 Guardian 19 with 1994 Evinrude V4 140HP
Former owner 1987 Montauk with 1998 Mercury 90HP
Nova Scotia

jimh
Posts: 4687
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: Fuel System Ground Wiring on c.1986 OUTRAGE

Postby jimh » Mon May 21, 2018 2:24 pm

You have will four wires length of 10-AWG wire with GREEN insulation. Use multi-strand tinned marine grade wire, not big-box store electrical wire. Each wire runs from one device to the next.

A to B
B to C
C to D
D to E

There will be a ring terminal on the each end of each of the four wires. Crimp the terminals. I also solder them, too, Cover with heat shrink to prevent water from having a path under the wire insulation and into the cable.

The ground point (E) can be the overboard anode (if one is still there) or the battery negative terminal primary bus if there is no dedicated anode. Again, if using the battery ground, be certain that circuit is bonded to the engine chassis and all the exposed metal anodes on the engine are bonded to the engine chassis.

I would use stainless steel hardware for the attachment points with star washers so the points of the star washers pierce the metal of the devices. Once everything is installed and checked for ultra-low resistance connections, paint over the connections with liquid electrical tape. You will then have an OEM-equivalent bonding system.

jimh
Posts: 4687
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: Fuel System Ground Wiring on c.1986 OUTRAGE

Postby jimh » Mon May 21, 2018 2:38 pm

If the fuel system has an electrical fuel tank level sender, try to keep the fuel tank sender circuit isolated from the bonding circuit. Usually the fuel tank level sender will have two conductors. Sometimes on of the conductors is bonded to the tank itself. That is not a good practice. The current for the fuel tank level sender is then flowing on the tank bonding circuit. A better practice is to use two wires to carry the fuel tank level sender circuit back to the gauge or instrument that will be sensing the tank level from that sender, and make the connection of the negative or low side of the sender circuit to the battery negative bus at the nearest power distribution panel. WIth that wiring, the fuel tank level sender current is not flowing on the tank bonding circuit.

Don SSDD
Posts: 107
Joined: Fri Oct 23, 2015 6:58 am
Location: Nova Scotia

Re: Fuel System Ground Wiring on c.1986 OUTRAGE

Postby Don SSDD » Mon May 21, 2018 4:00 pm

Thanks for the detailed information. I am using the original mechanical fuel level gauge which is under the clear plastic cover [on the cockpit deck] behind the console.
1986 Outrage 18 with 2001 Honda 130 HP
Former Owner 1991 Guardian 19 with 1994 Evinrude V4 140HP
Former owner 1987 Montauk with 1998 Mercury 90HP
Nova Scotia

jimh
Posts: 4687
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: Fuel System Ground Wiring on c.1986 OUTRAGE

Postby jimh » Tue May 22, 2018 1:44 pm

Below is a sketch showing two methods of bonding wiring. One method is to daisy-chain from device to device; shown on the left side. A second method is to use dedicated bonding conductors from each device to a central bonding bus, with the bonding bus then being wired to the ground reference point; this is shown on the right. Use one of the two methods, but do not combine them.

bondingWiringMethods.jpg
Two methods of wiring a bonding system: daisy-chain or bus. Pick one method and don't combine them.
bondingWiringMethods.jpg (37.71 KiB) Viewed 223 times


The BUS method is probably preferred but it uses a lot more wire. In the DAISY CHAIN method a loss of one contact could compromise the whole system by isolating more than one device.

Maintaining the integrity of the bonding system is very important. The action of flowing gasoline through the hose from filler inlet to tank can create an electrical charge. It is also imperative that the metal of the filler inlet not be raised above ground potential. When the filler hose is brought from the pump to the filler inlet, both the fitting on the hose and the filler inlet should be at the same potential--ground or zero volts--so there is no sparking.