A C180 FLOAT PLANE RAN OUT OF FUEL AFTER LNDG. THE PLT HAD FLOWN 28 HRS THE PREVIOUS 4 DAYS.

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THE ACFT WAS USED IN SEARCH AND RESCUE OPS FOR AN OVERDUE/MISSING ACFT. I DEPARTED ZZZ1 ON THE MORNING OF THE EVENT; AN XA00 ON A SEARCH FROM ZZZ1 TO ZZZ2; A DISTANCE OF APPROX 82 NM. WE ARRIVED AT ZZZ2 AT APPROX XD15; FUELED WITH 20 GALS; NOTED 25 GALS ON L; AND 20 GALS ON R FOR A TOTAL OF 45 GALS; AND DEPARTED AGAIN AT XE30 FOR A RETURN SEARCH TO ZZZ1. AFTER RETURNING TO ZZZ1 AT XI15 THE ACFT RAN OUT OF FUEL WHILE TAXIING TO THE DOCK. A UNITED STATES FOREST SVC BOAT TOWED THE ACFT TO THE DOCK. OUR PLANNED FUEL BURN FOR THE TRIP WAS 12 GPH. I HAD NEVER FLOWN THIS PARTICULAR C180 BEFORE; WHICH IS EQUIPPED WITH AN 0-470 ENG. MY EXPERIENCE WITH THE MODEL ENG/ACFT AND PWR SETTINGS IS 12 GPH FUEL BURN. THE DEVICE USED TO MEASURE THE FUEL QUANTITY SHOWED INCREMENTS OF 5; 10; 15; 20; ETC. I THINK THAT THE EVENT WAS CAUSED BY UNFAMILIARITY WITH THE PARTICULAR ACFT. OUR FLT VARIED FROM CRUISE SEARCH TO SLOWER SEARCHING WITH THE FLAPS DOWN AND POSSIBLE HIGHER PWR SETTINGS. AT SOME TIME DURING THE FLT THE FUEL GAUGES STARTED TO INDICATE FULL ON BOTH TANKS. MY EXPERIENCE HAS TAUGHT ME TO NOT TRUST FUEL GAUGES; AND USE MY WATCH AND KNOWN QUANTITY TO DETERMINE FUEL INFLT. THE ACFT WAS NOT EQUIPPED WITH A FUEL FLOW INDICATOR. I HAD FLOWN AS AN OBSERVER AND PLT IN VARIOUS ACFT (C180; C185; DHC2) FOR APPROX 28 HRS OVER THE PREVIOUS 4 DAYS. THE EMOTIONAL STRAIN; AS WELL AS FATIGUE; ARE DEFINITELY CONTRIBUTING FACTORS.