"Oh, by the way...." the boat's former owner said, as he handed me the key, ".... the fuel tank gauge doesn't work. Not sure whether it's the sender or the gauge." Ah blast - thought I - another "little" job. He told me how much fuel the engine burns per hour and that will help if I remember to record the hours every time we motor somewhere. Or I can do what at least two friends did to deal with the same problem: get a stick that would reach to the supposed bottom of their tanks, calculate the number of gallons a full tank would hold, mark the stick in units of one's choosing (usually gallons) and move on. I'm a bit more uptight than that about reliability and accuracy so I am considering replacing whatever has failed in the system. Components I can think of: sending unit, wiring and gauge. Is there anything else hiding in there? My real issue is the difficulty accessing and replacing the two terminal units, the sender and the gauge. I haven't investigated either but expect that like most items on sailboats, they will not be simple. Any words of advice (short of " hire a mechanic, stupid")? Anecdotes are even welcome. My research so far reveals a bunch of sending units and gauges available out there, none of which look "universal". On top of that the boat, a C&C 29 MK I, was re powered from gas to diesel some time ago and there don't seem to be a lot of associated service records in anyone's files. Words of advice joyfully accepted; commiseration appreciated; sympathy probably wasted - it's my own damned fault.