Fuel tank sending unit rebuild service

I'm running the Spectra unit in mine and I must have gotten lucky. This weekend it was reading 1/8th tank, so I stopped and filled up. It took 15 gallons to fill an 18 gallon tank and the fuel gauge moved to full when I was done. I don't trust it's accuracy below 1/4 tank so I try to keep it filled when it gets that low.