On July 2, 2001, about 0645 Alaska daylight time, a float-equipped Cessna 180 airplane, N4989A, was destroyed by fire following a precautionary landing at a remote lake located about 2 miles north of Houston, Alaska. The airplane was being operated as a visual flight rules (VFR) personal flight under Title 14, CFR Part 91, when the accident occurred. The solo certificated private pilot was not injured. Visual meteorological conditions prevailed, and no flight plan was filed. The flight originated at Willow Lake, Willow, Alaska, about 0630. During a telephone conversation with the National Transportation Safety Board investigator-in-charge on July 2, the pilot stated that about 15 minutes after departure, while in level, cruise flight, the engine began to run rough. He said that he elected to make a precautionary landing on a remote lake to investigate the engine problem. After an uneventful landing and while taxiing to shore, flames erupted from under the engine cowling, and quickly spread throughout the cabin of the airplane. The pilot was unable to bring the fire under control, and was eventually forced to abandon the airplane, and swim to shore. A Federal Aviation Administration (FAA) airworthiness inspector, Anchorage Flight Standards District Office, examined the airplane at the accident scene on July 5. The FAA inspector reported that the fire totally consumed the main fuselage, engine nacelle, and both inboard portions of the wings. He added that the engine eventually fell into the water, but was later recovered by the insurance adjuster during the recovery efforts. The inspector reported that due to the substantial amount of fire damage, he was not able to discern the origin of the fire. The pilot did not submit a Pilot/Operator report (NTSB form 6120.1/20).