Grounding your Fuel Tank and Fuel Fill

[sirg243]

Hey guys,

ive been restoring an old maxum speedboat over the last year and finally got it in the water in April. As i have been continuing to work on it, i noticed something i had not noticed before.
The ground off my fuel tank was not attached to anything. It was attached to the tank and the other end was not attached to anything. I also found a wire coming off my fuel fill, the part the cap screws into and this wire was sniped and not going anywhere. After reading up on it a bit i have found out that this not being grounded can be dangerous when filling the gas tank.

I had assumed i could just run these wires together, and then back to the negative on my battery and that would ground it. Is this Correct?

I had an electrican friend of mine come by and test it. When my battery for the engine is hooked up, he says we are getting 12v between the fuel tank and the positive of the battery. He says this means the fuel tank is already grounded and i dont need these wires. Does that make any sense? Or should I run these two wires back to my battery?

I have very little knowledge of marine electrical and have been learning as i move forward with this project. Any information would be appreciated.

 

[Scott Danforth]

the tank is to be bonded to the hull (usually a brass thru-hull) and the fuel fill and tie back to the engine block this is to prevent sparks when you fuel up.

there should be green bonding wires

should not matter if there is a battery or not.

 

[Chris1956]

A ground on the sender is necessary for the fuel level sensor to operate. Perhaps the fuel gauge is grounded and that ground is connected to the tank somewhere.

 

[sirg243]

A ground on the sender is necessary for the fuel level sensor to operate. Perhaps the fuel gauge is grounded and that ground is connected to the tank somewhere.

Yeah this was my thought actually. The guage does not function but maybe this is the case.

would it be smart to run this back to the negative terminal on my
Battery? This would make sure these things are grounded correctly?

 

[gm280]

If you have voltage running to the meter and no ground, how can it read anything? You need a complete circuit for it to work. The fuel sensor in the tank is a variable resistive connection, but it still needs voltage and ground to complete the circuit for the gauge to read anything. JMHO

 

[sirg243]

If you have voltage running to the meter and no ground, how can it read anything? You need a complete circuit for it to work. The fuel sensor in the tank is a variable resistive connection, but it still needs voltage and ground to complete the circuit for the gauge to read anything. JMHO

Thank you for your opinion. Appreciate it.

the wire from the fuel guage is not connected to anything. The gauge is not functional.

So since i have 12v from positive on battery to fuel tank, its grounded? No need to run these wires back to negative post? If I run it back to the negative post is it a better option just to be sure?

i just want to be extra safe when it comes to
Things like this. Definitely want to be sure

 

[Chris1956]

If you put the positive lead on a voltmeter on the battery positive, and the negative lead on the fuel tank, and get a 12VDC reading, the tank is grounded somewhere.

 

[76SeaRay]

Scott, is the bonding to a thru hull a requirement or an extra safety measure? My 76 Sea Ray didn't have that connection as it came from the factory. However, mine was originally an OMC drive so the engine had a direct connection path to water grounding whereas an Alpha One (which I will be putting in) has the sliding drive shaft connection to the outdrive and water grounding. I haven't seen a boat that uses a thru hull for grounding unless I just didn't see it. I would guess those that don't rely upon the engine grounding through the sterndrive.