Help with gas tank ground wiring (gas gauge troubleshooting)

[JUST JOHN]

So I traced my in-opp gas gauge to a bad ground at the sender/tank. After cutting up my newly caulked hatch for access to test, welp. I jumped the ground and saw my gas gauge at 'F' for the first time in almost two years. It worked intermittently before last season.

The gauge and sender check out per the procedures outlined here:
https://www.jamestowndistributors.co..._Reference.pdf

My question is with regards to the ground wiring on my '77 OB Seafari 20:




Does the front ground wire just go to the filler flange? Or...?

As you can see there is only one wire on the sender and it grounds to the tank via screws. There is however a tab on the sender flange that I'm thinking may benefit from an additional ground wire... Thoughts? Where would I run it to?

I traced the rear two (power/ground) wires to the rear battery compartment... Ideally I'd replace all these old wires if I can trace them all down. Any recommendations? Please confirm where these wires go... I ran out of daylight and it's a little crowded in there w/ the oil tank, battery, and water separator under the rear starboard seat hatch. I'm sure the + wire runs up the starboard side loom to the gauge. If I can do this in stages so I can get the floor buttoned back up soon, all the better.

This thread had good relevant information regarding grounding:
http://www.classicseacraft.com/commu...ht=tank+ground

Any help or guidance would be greatly appreciated.

[jtharmo]

I re-grounded the sending unit on my yellow Seafari from the sending unit lug directly to a negative bus in the back. A bonding circuit has a different purpose then the ground side of an electrical circuit. For that reason and because it's so easy to run a wire to the back I thought it best to run a ground to the negative side of the battery.

[SailorChlud]

I second SSP Bill above, and will add that you should check the underside of the sending unit before screwing it in - mine had a small U-shaped metal piece (horizontal) that was where the float electrical connection was, and it had been bent in the factory so that the tops of the U were touching - giving me a false reading. It always read 1/4 full, until I separated the U wings and then it had the correct resistance.

[JUST JOHN]

Thanks guys.

What gauge wire did you run for the sender ground? EDIT: I bought 14 AWG. I had access to many free options at work, but opted to buy something in the correct color.

Can you confirm whether that tank ground wire running along the filler tube forward is the ground for the filler flange? Just trying to understand what everything is while I have it open...

[jtharmo]

I think I used 16 gauge for ground and to the gage but I may be wrong. 14 gauge will handle 10-20 amps anywhere on a Seafari. That’s well more then a gage and sending unit will draw. You should be fine with that. I only pulled the little panel to access the sender. I didn’t see the bonding wires.

[SailorChlud]

I used 14 guage wire. If you have a metal filler that has to be bonded, I would use the same wire from the filler screw to the tab on the tank. I have a Perko plastic filler/vent cap combo, so did not bond the tank to the filler, just the tank to the negative bus in the rear of the boat. Use the diagram below, which if for a plastic tank, but it shows all the appropriate connections. With an aluminum tank like we have, the bonding wire from the filler goes to the tab welded to the tank, not the sender screw.

[JUST JOHN]

I ran the new ground from tab on sender to the negative battery terminal and have a working gas gauge again. I'll be replacing all the old connectors on the existing tank grounds this afternoon and coating in dielectric grease. I'm sure that forward running wire is in fact the ground for my original metal filler flange.

[SailorChlud]

Sounds like the job is coming along! I will hopefully be out on Raritan Bay this afternoon for a little dinner jaunt. Hope you get some boating in this weekend.