PLT OF AN SMA SEL ACFT MADE FORCED LNDG OFF ARPT WHEN THE ENG QUIT DUE TO FUEL STARVATION.

Narrative

I DEPARTED LAKE HOOD; AK; FOR BIG LAKE; AK; TO PICK UP A FRIEND IN AN SMA SEL ON MODEL X FLOATS. WE DEPARTED BIG LAKE AT XA00 AM; FILED A FLT PLAN; AND GAVE FSS WX RPTS 3 TIMES ALONG THE 300 NM RTE. I DROPPED HIM OFF AND STARTED AT ANOTHER 104 NM STRETCH. 62 NM AFTER LAST DEP; MY ENG STARTED TO SPUTTER. I HAD THE FUEL SELECTOR ON THE R TANK AT THIS TIME. MY CORRECTIVE ACTIONS WERE TO SWITCH THE SELECTOR TO THE L TANK AND THEN GIVE BOOST WITH BOTH THE HIGH AND LOW BOOST PUMP. THE ENG STARTED BUT ONLY FOR APPROX 5 SECONDS; THEN DIED AGAIN AND MY NEXT 2-3 ATTEMPTS TO RESTART THE ENG (TIME ELAPSE 20-35 SECONDS) WAS UNSUCCESSFUL. FORCED LNDG WAS NECESSARY; AND WAS MADE SUCCESSFULLY WITH LITTLE DAMAGE IN A SWAMP. NTSB CALLS IT AN INCIDENT. AFTERTHOUGHTS: I WAS LOW ON GAS IN THE R TANK WITH APPROX 10 GALLONS LEFT IN THE L TANK. AIR MIGHT HAVE BEEN SUCKED IN THE FUEL LINE; AND MY TIME FOR RESTART AND ALT OVER GND WAS LIMITED; BUT EARLIER EXPERIENCE TOLD ME THAT THE ENG SHOULD HAVE STARTED. AFTER MY CALCULATIONS; THERE SHOULD HAVE BEEN ANOTHER 16 GALLONS OF GAS AFTER THIS 3.7 HR TRIP (80 GALLONS FULL TANKS; 6 UNUSABLE). TURB MIGHT HAVE BEEN A SMALL FACTOR; AND I AM SURE THAT IF THERE WOULD HAVE BEEN PLENTY OF GAS IN BOTH TANKS THIS INCIDENT WOULD NEVER HAVE OCCURRED. BUT STILL; WHERE DID ALL THE GAS GO; AND WHY DID IT NOT RESTART?