Fuel gauge reads inverted

[tkaustin]

This is a 2011 25SC. The fuel gauge reads inverted. The boat is new to us. The first time I put fuel in it, I brough itt up to about half full. That 4 day weekend cruising, the gauge indicator gradually rise from a bit under half full to more than half full. I know these boats are easy on fuel, but I don't think they actually producer more diesel. Anyway, I've now filled the tank and the gauge reads nearly empty. Clearly some wires are incorrectly hooked up. How can I access these wires, or otherwise locate them?

 

[knotflying]

I am not familiar with the ins and outs of the 21, but it sounds like if you can access the wires at the unit at the tank or at the gauge you can just reverse the wires.

 

[tkaustin]

Thanks knotifying. The boat is however a 25 and is 4 years old. There is no fuel gauge per se as it reads from the yanmar control panel snd from the Garmin unit.I would be very surprised if there are any wires from the actual fuel gauge that proceed to the instrument panel. It seems they go to the electronic control unit.

 

[Brian B]

I have a 2010 25SC. You can access the sending unit wires through the hatch on the front of the step. Fuel shut off valves are there also. Do you know if it has always read in reverse from the previous owner or is this something new?

 

[knotflying]

Thanks knotifying. The boat is however a 25 and is 4 years old. There is no fuel gauge per se as it reads from the yanmar control panel snd from the Garmin unit.I would be very surprised if there are any wires from the actual fuel gauge that proceed to the instrument panel. It seems they go to the electronic control unit.

Sorry abut that. For some reason I thought I read R-21. Check the leads out of the fuel sensor at the tank. If they are pre-connected then check the leads at the wire harness. The harness should be a large group of wires coiled up onthe port side in the engine compartment. Usually it is near the fuel filter. There are several leads and they should be marked for what they are for. There will be some that are for add on modules and are not even connected. Sounds like someone reversed the connections. A simple switch of the wires should fix your problem.

 

[Hydraulicjump]

I'm a bit confused. Is the inverted reading on both the Yanmar gauge (notoriously inaccurate) and the Garmin display? My Garmin calculates fuel usage and I give it fuel input, not relying on the tank sending unit (I think). So I find it odd that both gauges would be screwed up since they use different sources of information. What am I missing here?

Maybe you really do have a magic Ranger Tug that makes fuel as it goes!

 

[tkaustin]

The Garmin fuel calculation is believable. After fill up it read 80 gals, and is gradually decreasing at a believable rate. The gauge reads out in two places. The Yanmar panel and the fuel level presented by garmin as a percentage. Both of those, after filling up the diesel tank to full indicated about 10% remaining. As we cruise, they indicate more fuel.