Do a search "fuel gauge" and you will find tons of info on this. http://www.seadooforum.com/showthread.php?t=6138&highlight=fuel+guage
This one will give you a good start. First do gauge test to determine if you guage is good or not. If good i would bet its just a bad float. ohm the 2 wires going into the baffel. If you get any reading and your guage reads empty its your float setting at the bottom of the baffel. Cheap fix. If you get no resistance reading on your ohm test its the F1 fuse. Give it a try. you can do all this without taking anything apart. CCC