SUSPECTING LOW FUEL; SMT FLOAT PLANE LANDS ON OPEN WATER TO INVESTIGATE PROB.

Narrative

I PREFLTED MY SMT ACFT AT KETCHIKAN INTL ARPT DOCK AND WARMED IT UP. WHILE WARMING THIS ACFT; I OBSERVED THAT I HAD 24 GALLONS IN MY FRONT TANK AND 12 GALLONS IN MY CTR TANK. I TOOK OFF FOR KETCHIKAN AIR HARBOR DOCK ON MY FRONT TANK. AFTER REACHING THE HARBOR DOCK I LOADED MY ACFT FOR A 15 MIN FLT TO METLAKANA HARBOR. AGAIN; I TOOK OFF ON THE FRONT TANK WITH 24 GALLONS. ABOUT HALFWAY THERE I SWITCHED TO MY CTR TANK WHICH HAD 12 GALLONS TO BURN MY EXISTING FUEL IN THAT TANK. ABOUT 5 MINS LATER MY LOW FUEL PRESSURE LIGHT WENT ON AND I PROCEEDED TO HAND PUMP MY WOBBLE PUMP IN ATTEMPTS TO BUILD MY FUEL PRESSURE. THIS DID NOT WORK. I MADE RADIO CALL TO MY COMPANY AND INFORMED THEM OF THE PROB AND MY LOCATION. AT THAT POINT; I CHKED AGAIN TO SEE IF I HAD FUEL. MY CTR TANK WAS STILL SHOWING 12 GALLONS. AT THIS POINT I HAD TO MAKE A DECISION TO CONTINUE TROUBLE-SHOOTING THE PROB OR PREPARE FOR A DOWNWIND LNDG IN OPEN WATER WITH 3 PEOPLE ABOARD. AFTER THE LNDG; I AGAIN TRIED TO DETERMINE THE CAUSE OF THE PROB. I GOT OUT ON THE FLOATS AND CHKED THE ACFT. AT THAT POINT I ATTEMPTED A RESTART ON THE FRONT TANK. THE ENG STARTED AND I CONTINUED TO METLAKANA TO DROP OFF MY 3 PAX. I FLEW BACK TO KETCHIKAN ALONE AND WHEN I RETURNED THE CTR TANK WAS INDICATING EMPTY. AFTER TALKING WITH SEVERAL PLTS AND THE MECH; I WAS INFORMED THAT THESE TYPES OF TANK GAUGES HAVE BEEN KNOWN TO STICK.