On August 5, 1995, at 1930 Alaska daylight time, a float equipped Piper PA-18-160 airplane, N814JM, registered to and operated by the pilot, lost 9.5 inches of a propeller blade and the pilot was forced to land the airplane approximately 15 miles northeast of Port Alsworth, Alaska. The personal flight, operating under 14 CFR Part 91, departed Port Alsworth for a local game spotting flight. No flight plan was filed and visual meteorological conditions prevailed. The commercial certificated pilot and the passenger were not injured and the airplane was substantially damaged. According to the pilot, during cruise flight the engine began to vibrate severely. He closed the throttle and pulled the mixture to the idle cutoff position. He pushed the nose of the airplane toward the ground and landed in the alder bushes. The airplane nosed over. Examination of the airplane showed that 9.5 inches of one propeller blade was missing. Examination of the airplane records showed that the propeller had been straightened on September 30, 1994. The pilot stated during a telephone conversation on August 7, 1995, that the propeller had sustained a "propeller strike." The copy of the yellow tag submitted by the pilot showed that as a result of the propeller strike and resulting blade tip damage, the propeller had to be straightened and cut to 80 inches. The pilot also had the blade pitch angle changed to 45 inches. The pilot did not submit the propeller for examination as requested.