On August 18, 2013, about 1000 Pacific daylight time, a Cessna 172B airplane, N8141X, sustained substantial damage following a loss of engine power during cruise flight, and ditching in a remote mountain lake, about 18 miles northwest of Sisters, Oregon. The airplane was registered to a private individual and operated by the pilot as a personal local flight, under the provisions of 14 Code of Federal Regulations Part 91. The private pilot and the three passengers were not injured. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed. The flight departed the Lebanon State Airport, Lebanon, Oregon, (S30) about 0745. During a telephone interview with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on August 22, the pilot said that he and his passengers had flown to the remote area to scout potential camp sites for an upcoming trip to the area. During the return flight to the airport, the engine abruptly lost power. He was able to restart the engine, and suspecting the possibility of carburetor ice, he used carburetor heat. The engine ran for about 5 minutes, and abruptly lost power again. He again was able to restart the engine, which ran for 2-3 minutes before losing power for the third time. He restarted the engine, but it ran for less than one minute. He was unable to restart the engine. The pilot was flying over heavily wooded, rugged terrain, and elected to ditch the airplane in a Lake. He prepared the airplane and passengers for the ditching. After the airplane came to rest in the water near a shoreline, the pilot and passengers exited the airplane as the cabin filled with water. After a short rest, while holding on to the wings of the still floating airplane, all the occupants of the airplane successfully swam to shore. The airplane sank in about 8 feet of water, coming to rest on the bottom of the lake, with its tail sticking above the surface. According to the pilot, the airplane is owned by another family member, and they have been flying it for the past 3 to 4 years. He said there were no known mechanical problems with the airplane prior to the accident. The airplane was eventually recovered from the lake, but its engine was not preserved to prevent corrosion. Despite repeated requests, the operator/pilot did not submit the NTSB Form 6120.1 PILOT/OPERATOR AIRCRAFT ACCIDENT/INCIDENT REPORT.