On December 27, 1994, at 0806 central standard time, a Cessna 150H, N6417S, was destroyed during a forced landing near Monahans, Texas. The airplane, owned and operated by the passenger, had just departed from the airport on what was to have been a local personal flight. There was no flight plan filed and visual meteorological conditions prevailed. The commercial pilot and the pilot rated passenger sustained serious injuries. In a written report submitted by the pilot, he stated that he planned the flight to check the engine recently installed. He further stated that he performed a pre-flight and executed a "normal" takeoff. During the initial climb (200 feet above ground level) and at a point close to the end of the runway the engine began "running rough." Power was reduced so that he could land on the remaining runway. The rated passenger checked the fuel mixture shortly after the engine began to run rough. When the pilot realized that he could not make the runway he "added full power and levelled off at his current altitude." After levelling off the engine began to lose power as the pilot executed a left descending turn and added 20 degrees of flaps in preparation for landing. Both the pilot and passenger reported that at some point they both heard the stall warning horn. The pilot stated that "touchdown was very hard and the ground roll was very short due to the low airspeed." Following touchdown, the aircraft slid sideways into a fence, around a gas pipe line. Following the impact with the fence the aircraft was consumed by fire. The pilot further stated that he thought "he had experienced carburetor icing." No evidence of carburetor heat being applied was found and the pilot did not report that he had used it. An examination of the aircraft records revealed that the engine was installed on December 26, 1994 (date of sign off in log books). A physical inspection of the engine revealed that the rocker arms were installed incorrectly. It was noted that the engine would not rotate because the thrust flange was broken and pushed to the rear. The carburetor assembly melted off of its mounting point. Inspection of the oil pump revealed that it rotated freely. Temperature at the time of the accident was reported to be 45 degrees and the dew point was 43 degrees. A review of the icing probability chart established that the aircraft was operating in an area of serious icing conditions.