See tanksinc.com for an inexpensive ($69) fuel gauge calibration unit. It can be used for 4 calibration points and allows you to calibrate the amount of fuel in the tank (independent of fuel tank shape) to the gauge. Since our tanks are often not rectangular in all 3 dimensions, any sensor that relies on depth of fuel in the tank is at best an approximation. Apparently this gauge calibrator changes the resistance (reported by the sender to the gauge). Thus, you set the gauge to empty when the fuel is just at the pick-up, set it to 1/4 when you know the tank is 1/4 full, set it to 1/2 full when you know the tank is 1/2 full, etc. for 3/4 tank and full tank. It requires 12 volts but has battery to store the calibration points I think--have not installed it yet. FWIW--especially for those who care about the fuel in their tank and can't (or won't) keep up with the hours and gallons/hour, etc. Charlie NelsonWater Phantom1995 C&C 36 XL/kcb
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