On August 30, 1996, at 1530 Alaska daylight time a wheel equipped Cessna 180 airplane, N8241V, registered to and operated by Lake Clark Air Inc., experienced a loss of engine power and subsequent forced landing while en route from the Mulchatna River to Port Alsworth, Alaska. The air taxi flight, operating under 14 CFR Part 135, departed the Mulchatna River area with two hunters on board. The destination was Port Alsworth. No flight plan was filed and visual meteorological conditions prevailed. The certificated airline transport pilot was not injured, one passenger sustained serious injuries and one passenger received minor injuries. The airplane was substantially damaged. According to the passengers' statements, the pilot drained approximately 50 gallons of fuel from the airplane after landing. They said the pilot drained the left fuel tank dry. The operator stated that the airplane holds 84 gallons of fuel. It is their practice that upon reaching a field site, they drain the left fuel tank and store the fuel for future use. As a result, the company practice is to operate the airplane's fuel selector valve in the right fuel tank position. According to the passengers, the pilot did not dip the fuel tank prior to departure. They stated that he did not give them a passenger briefing prior to departure. The passengers indicated that the flight was turbulent. While in cruise flight, and 5 minutes from the destination, the airplane's engine stopped producing power. The propeller continued to windmill during the descent. The pilot indicated on the NTSB Form 6120.1/2 that he applied carburetor heat, pushed the mixture full rich, pushed the throttle full forward, and placed the fuel selector in the "both" position. He landed the airplane and during the landing roll the airplane "flipped" over. Subsequent examination of the airplane on September 4, 1996, by Federal Aviation Administration Flight Standards District Office Inspector, Mr. Gerald Martelli, showed that with the airplane in a level attitude there was only 7/16 of an inch of fuel covering the bottom of the right fuel tank. The fuel was drained from the right fuel tank through the gascolator. A total of 7.3 gallons of fuel was drained. The left fuel tank was drained through the gascolator and it yielded 3.1 gallons of fuel. The fuel was returned to their respective tanks and the engine was started. The engine started and operated normally.