Issue with Garmin Fuel Gauge

[Eachtra 27]

I have filled up twice since taking possession of our new (to us) 2021 R27. Both times the Garmin chart plotter showed approximately 40 Gallons in the the tank. Both times I was expecting to require 110 gallons but only required 70 gallons. The chart plotter is an 8612. I have twin 150 hp Yamaha. I am hoping this is a silly question and there is a quick calibration I can do. Any advise would be appreciated. Thanks,

Sean

 

[Maggie Anne]

I've found the garmin fuel used values to be pretty accurate, At the start of the season, I fill the tank to full, which I determine to be when I can see the fuel level a few inches below the filler cap, then set the fuel on board to 150 gallons. After which I usually don't fill up to full anymore and just rely on the fuel remaining indication. I have found a slight discrepancy between the garmin fuel used value and the actual fuel used with the garmin reporting about 1% greater use than actual. With a 40 gallon discrepancy between your fuel on board (40) and the 70 gallons it takes to fill the tank, I would guess that maybe the initial fuel on board was inaccurate? So instead of 40 you really had 80?

 

[Eachtra 27]

sorry, just re-read my post, and I was a little unclear. I started with a full tank and 150 gallons on the Garmin. Both times the Garmin unit showed 40 gallons remaining. Both times I only required 70 gallons, not 110 gallons as expected. I agree, on my previous R25, the Garmin was very accurate. Thanks for taking the time to reply.

 

[Full_O_Fish]

You should check your NMEA2000 device list and see what source is being used for your fuel calculations, whether it's the Yamaha gateway or dedicated Garmin GFS-10 fuel flow sensor(s). Could be that your engines or rates are double reporting on the network, or your K-value (for fuel flow rate offset) may be inaccurately programed.

There are plenty of other options such as having the fuel remaining calculation set to read from a tank sender rather than continuously calculate from a flow sensor.

If you have a Yamaha gauge in addition, does the expected fuel burn show accurately there?

 

[Eachtra 27]

Great info, thanks for sharing. At sea trial we were told the garmin provided the most accurate data and even removed the fuel gauge from the Yamaha combo.

Sean

 

[Full_O_Fish]

Yes, the Garmin system can be exceptionally accurate, but only to the extent of what data it receives and how it processes it. If you get the actual Yamaha page on your Garmin display then you should at least have the gateway on the network, and the data the Garmin system receives is only as accurate as whatever each engine is outputting (calibrations and offsets are set within the Yamaha system) and accuracy is based on the expected fuel output of the injectors at each rpm. If you had the Garmin fuel flow system, each flow and tank sender is calibrated individually in the Garmin system and is calculating actual fuel flow rate through the lines.

 

[Mike and Sarah]

Sean,
One thing that’s different than pretty much every other R27 and yours is the twin 150s. I’m curious if there is a different calibration that needs to happen with twins vs a single 300. Might be worth a call to Garmin.

 

[Eachtra 27]

thanks Mike, great point. I am working with Port Boat House on solutions, but seems to have many stumped.