Garmin vs Penta fuel gauges

[Todd Tugnut]

I have ‘23 R31-CB. When I fill with fuel, I go to the Garmin and push “Fill All Tanks”. Both Garmin and Penta displays reset to 180 gallons. When I burn about 20 gallons, Garmin shows 160 and Penta is still 180. At some point, Penta starts to show fuel being consumed and begins to tick down, but always shows about 20 gallons more than Garmin. What’s goin on here?

 

[dbsea]

The garmin isn’t reading the tank by default, it’s using consumption data to estimate fuel remaining. The Volvo has a reed style sensor in the tank, but they are usually not calibrated as precisely as they could be plus the sensor is in the aft of the tank. It’s never going to be perfect…

 

[Mike and Sarah]

Also the Volvo gauge will only be close to accurate when the boat is sitting still and flat in the water. Volvo gauge will read 180 while the bow is raised as in cruising. Even when you have actually consumed say 50 gallons.
We just go by the garmin. Garmin display has been very accurate. It maybe off a couple gallons in the winter when we are using the Webasto as that fuel is not metered.

 

[mlanger]

Also the Volvo gauge will only be close to accurate when the boat is sitting still and flat in the water. Volvo gauge will read 180 while the bow is raised as in cruising. Even when you have actually consumed say 50 gallons.
We just go by the garmin. Garmin display has been very accurate. It maybe off a couple gallons in the winter when we are using the Webasto as that fuel is not metered.

This is what I’ve also seen. The Garmin fuel gauge, when you accurately reset it after refueling, is far more reliable than the engine fuel gauge. My engine fuel gauge always reads high, sometimes as much as 40 or 50 gallons. I never rely on it. (My boat is very stern heavy.) I always rely on the Garmin. When I refuel, I can normally fit in within 1 gallon of what the Garmin says I can add. for example, if the Garmin says I have 90 gallons left in my 145 gallon tank, I can normally put 55 gallons of fuel in. It’s that accurate.