Aluminium fuel tank earth

 Hi everyone ,

im hoping that some of you guys who are way more experienced than myself can clear up a doubt that I am having with my boat? 

In a glass boat - should an aluminium fuel tank be grounded to a negative battery terminal ? 

Not sure if it matters but the fuel tank does have a sender hooked up to digital gauges ?

Thanks in advance 

Joel 

 


scano's picture

Posts: 1066

Date Joined: 31/05/07

My thoughts would be yes

Mon, 2018-04-16 12:06

 Mainly because how else do you get a completed circuit for the gauge to read correctly? You obviously have the power wire going into the fuel tank sender unit, but you need an earth wire to complete the circuit. 

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Posts: 109

Date Joined: 08/05/09

That gauge

Mon, 2018-04-16 12:27

 the gauge is connected via two wires and works spot on - what I am more curious about is whether the tank should be grounded to reduce the risk of ignition ?

 

ranmar850's picture

Posts: 1962

Date Joined: 12/08/12

tanks can be grounded

Mon, 2018-04-16 14:15

 The wire will go to the filler neck to reduce the risk of static spark, or am i wrong? I have to investigate this myself, the new boat has a sender unit installed, but no gauge fitted, probably won't bother.

squidvicious1's picture

Posts: 610

Date Joined: 22/07/10

 I’ve got a fibreglass boat

Mon, 2018-04-16 16:28

 I’ve got a fibreglass boat with a metal tank and only have the 2 wires coming out of the floor going to the gauge.

just dhu it's picture

Posts: 1068

Date Joined: 14/05/09

No earth

Tue, 2018-04-17 06:38

 the boat is glass and no potential between tank and glass body , as ramnar said the only earth would be for static prevent but in most cases now they use anti static plastic as the filler and tank are only connected via a rubber hose,  the sender unit is a resistor and only requires two wires , where as your gauge will have the positive and negative connected , ie the sender acts like a switch in the circuit

 

 

Posts: 2874

Date Joined: 03/03/10

not sure you are correct

Sun, 2018-04-22 20:10

 resistor type level sensors are very old school , more than likely the fuel tank will have a "smart"or "hart" level transmiter which works by sending a 4 to 20 milli amp signal to the  fuel tank indicator  , personaly  i wouldnt earth the tank , the earth wire could build up a capacitance charge and if it becomes open circiut it could draw an ark and if there is any fuel vapour present there would be the potential for an explosion

  

ranmar850's picture

Posts: 1962

Date Joined: 12/08/12

That would probably explain

Tue, 2018-04-17 07:54

 The black and white wires protrudng from the wiring harness down the back; power connections to sender? I may fit a gauge, as a backup and crosscheck to the electronic monitoring. I still have a TINY bit of room on the dash.

just dhu it's picture

Posts: 1068

Date Joined: 14/05/09

Gauges

Tue, 2018-04-17 17:41

 Depending on your motor choice. Most motor gauges now have the dual level indicator as one of their views that you can scroll through so seperate fuel gauge won't be required

Stevo81's picture

Posts: 1073

Date Joined: 16/04/12

Once networked, your Axiom

Tue, 2018-04-17 18:59

Once networked, your Axiom will be able to show you fuel remaining in Litres. Tell it your tank size and when you have filled it and it will calculate back from the engines ECU fuel burn. Mine is near on perfect. 

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ranmar850's picture

Posts: 1962

Date Joined: 12/08/12

Can't get my Merc to talk

Sun, 2018-04-22 19:35

 Plugged in to the NMEA 2000 cable coonector to the gateway, removed the fuse that it says to remove if powered by NMEA 2000, and into the backbone, Axiom can't see the motor. Gateway is set to NMEA 2000, transmit, nothing doing. I am running Mercmonitor, not a VV. Any ideas, Stevo? all the other networking appears fine.

Posts: 109

Date Joined: 08/05/09

Thanks everyone

Wed, 2018-04-18 08:52

 thanks for your input guys !

ranmar850's picture

Posts: 1962

Date Joined: 12/08/12

Thread resurrection

Thu, 2018-07-26 21:04

 May  as well, as start a new one. I have the fuel manager working on the Dashboard app of either Axiom, works on fuel flow and you manually entering any fuel added. Fine, but what if you get siphoned? Fuel manager won't know, could be embarrassing. Sender is installed in tank already. I see a common type of fuel gauge reads from a 30-240 ohm sender--is this a really common size, or are there others? Tank is pretty empty ATM, so I can put an ohmmeter across to check? 

As to my complaint above that the Axiom couldn't "see" the motor during setup, well, it still can't when you go through that process, but all your engine Info is on the Dashboard already. You just can't get it as a sidebar, just full or splitscreen. Although I did see something tonight on THT that clears up a question--with the Merc, you can use either fuel flow or fuel level, not both, on an MFD. From a Merc dealer 

 

www.thehulltruth.com/marine-electronics-forum/949181-merc-150-four-stroke-circuit-diagram-fuel-level-sensor.html