Speedo and fuel gauge failure

[aceranch1]

I’ve got a year old G3 Sportsman. I understand it has a warranty but it’s the wrong time of year to put it in the shop. The other day while out on the lake I noticed my fuel gauge was pegged at totally empty. I panicked especially since the 22 gal tank was full when I set out. I opened the hatch and confirmed a full tank. I started for the dock as a precaution and noticed the speedometer was dead as well. These are on the same gauge. My separate tach and tilt gauge were good to go as were my other electronics. I checked the hot input on back of the gauge with a multimeter using the boat as a ground and it was getting 12V. That tells me either bad gauge or possibly bad ground from the gauge, does that sound right? Any suggestions please! Thanks!!


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[DaleH]

Ouch ... you can GROUND to your boat ... ?!?!?!? Yikes ... you don't want that, it's not the same as a car ...

Try an independent ground to a Negative feed to a buss under the helm, to the gauge.

 

[DaleH]

FYI, yes ... outboards are directly connected to the hull via the clamp bracket. But outboards are directly connected (electrically seperate) to the battery and are somewhat isolated from the hull. Many have specific instructions not to use the hull as a ground. The outboard mfg'rs want the connection direct to the battery.

Aluminum boats should be grounded like any other boat, but NOT to the hull of the boat.Outboards are not the same alloy as aluminum as hulls. Outboards are a highly defined alloy of aluminum, enough so as to make them a dissimilar metal to an aluminum hull alloy. Keeping them seperate (electrically) reduces the chances of galvanic action. An aluminum boat is a potential 'hot bed' for electrical activity (or injury) and can be quickly and drastically corroded if exposed to electrical currents for too long.

 

[MrGiggles]

The hull will likely have continuity to battery negative, it is common for manufacturers to use the engine block as a ground for the engine electrical, and there will usually be some sort of connection made through the swivel bracket and the hull. That said, there should always be ground wires ran all the way back to the outboard, you don't want to use the hull.

Outboard gauges are typically daisy chained from a single power and ground source that comes from the control harness. Since some of your gauges work it should be pretty easy to isolate where the problem lies. You need to check for power and ground at the gauge though, not the hull.

If power and ground are present, then you should run a resistance test between the fuel signal wire and ground. It should have a specific reading at full. If you don't have that, then you should do the same thing at the sending unit on the fuel tank. If the reading is correct there, you have a problem in the harness, if it is not, the sending unit has failed.

 

[aceranch1]

Good to know about the ground. I was referring to the black lead from my multimeter so no harm I assume. So I was able to pull the gauge out far enough to see all the wires, two yellows, one blue, one red, one black. I tested the red and black and only got 10.26 volts.


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