On July 31, 2007, about 1530 Alaska daylight time, a float-equipped Cessna 185E airplane, N70020, sustained substantial damage when it collided with trees during an emergency descent/landing, following a loss of engine power during cruise flight, about 6 miles southeast of Talkeetna, Alaska. The airplane was being operated by the pilot as a visual flight rules (VFR) cross-country flight in conjunction with his fish guiding service under Title 14, CFR Part 91, when the accident occurred. The commercial certificated pilot and sole passenger were not injured. Visual meteorological conditions prevailed, and no flight plan was filed. The flight departed Stephan Lake, Alaska, about 1500. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on August 1, the pilot said he was flying from Stephan Lake to Lake Hood, Alaska, cruising at 2,500 feet msl, and was about 20 minutes into the flight when the airplane's engine went to idle rpm, and the airplane started to descend. The pilot said he pushed the throttle forward, and he thought the engine rpm increased slightly, then returned to idle. He said he had turned the airplane toward a lake, but it descended too rapidly, and he landed in trees short of the lake. The airplane sustained extensive damage to the wings and fuselage. The pilot said that the airplane had sat on the water at Stephan Lake for two days prior to the flight, and that he drained the fuel tank sumps prior to takeoff. He said the airplane's fuel tanks were half-full on departure, which was more than enough fuel for the trip. The pilot said that there were no known mechanical problems with the airplane prior to the flight. After being recovered, the airplane was examined by a certificated aircraft mechanic. The mechanic discovered that the support shaft for the throttle and mixture bell cranks was missing. The air induction box assembly was examined by the IIC, and it was discovered that the air box had been repaired with incorrectly substituted parts. The air box (PN 1650012-1) installed in the accident airplane was the correct air box, however, a weld repair had been performed around the shaft support bushings on both sides of the box. The correct solid shaft bushings had been replaced with earlier generation roller bearings. The inappropriate installation did not allow for the support shaft to be properly pinned in place, and did not allow for the redundant safety of the correct installation, which would preclude the shaft from migrating out of the air box if either shaft end spacer were missing. An examination of the airplane's maintenance log books did not reveal any entries pertaining to the air box repair.