Fuel level reading

[fmstuart]

2020 Cutwater 32’ CB with twin Yamaha 300s. The Garmin “Remaining Gallons” indicates 215 gallons remaining. The Yamaha display shows what the attached picture indicates. The generator draws from the starboard tank. We have not used the generator much, so I doubt the display is correct. Could the float in the starboard tank be that off?

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[BB marine]

It is my experience that the sending units are generically calibrated by the factory. In order to have the fuel tank sending units read correctly they must be calibrated. When I purchased my C26 the fuel tank sending unit (single tank) was inaccurate. I was told just use the Garmin. I like checks and balances. I don't like something that is installed and doesn't work properly. I was talking to a service technician at the marina where I store my boat. I asked what the owners think of the inaccurate Volvo fuel gauges? His response was (WHAT ?) Prestige, Fairline, Jeanneau, and Volvo recommend that we confirm the calibrations are done properly and accurate. He explained to me how to do it. I posted a thread on how to accurately calibrate the sending unit. viewtopic.php?f=18&t=10780&hilit=+calibrate#p74140.
Slightly different resistance numbers/gallons for you tank capacity but the theory is the same. My sending unit reads worst case 3 gallons off best case I have had .8 gallons off from actual. I get better accuracy from the sending unit than the Garmin after the first 10 gallons used ( I'm not concerned when 9/10th full).

Sorry for the long history in my explanation. Yes probably sending unit is off that much. I would fill the tanks and confirm and start keeping a good log until you figure out how to maintain accurate fuel amounts onboard. Check to make sure (if possible though valves) that the fuel for both engines is not being pulled from one tank.

 

[fmstuart]

Thank you so much. I’ll post the results.


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