I have an older sailfish, 1992 252 model. Boat has two fuel tanks each with their own fill as well as a valve in the transom to switch from main to aux. Tanks are listed as holding 101 gallons. I have never put more than 75 gallons in either tank, no reason other than not carrying the weight and not needing that much fuel. Recently I was filling up for a longer trip; dock fuel pump starts getting high towards 90 gallons, my records should have put me at full right there + or - a bit. Well it keeps filling until I stop it at 108 gallons. My question is are the tanks somehow interconnected? I'm a bit confused on how this works; any comments, tips, advice is greatly appreciated.