On July 27, 2014, about 1045 Pacific daylight time, an Ercoupe, 415-C, N2013H, sustained substantial damage during a forced landing following a reported loss of engine power during cruise flight near Susanville, California. The commercial pilot and passenger sustained minor injuries. The airplane was registered to and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no flight plan was filed for the personal flight. The local flight departed Rogers Field Airport (O05), Chester, California, about 0940. A family member of the pilot reported the airplane overdue to local law enforcement on the afternoon of July 27, 2014, after becoming concerned when the pilot had not arrived at his planned destination. The Federal Aviation Administration (FAA) issued an Alert Notification (ALNOT) for the missing airplane. The wreckage was located by law enforcement personnel about 1922 on July 27, 2014, in rugged terrain. In a written statement to the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), the pilot stated that during the first flight leg that day, the airplane primer was used during a cold engine start. The next flight was the accident leg, and due to the short period the engine was shutdown, the primer was not used for engine start during this leg. On the accident flight, the pilot stated that while in cruise flight about 6,500 feet mean sea level (msl), he began a slow climb to cross a ridgeline and as he pushed the throttle up, the engine did not respond. He pumped the throttle numerous times and the engine finally responded but the airplane had lost altitude and airspeed and he was forced to land the airplane in a wooded area. Subsequently, the passenger and him egressed and hiked to safety. Utilizing the weather conditions at the nearest reporting station, the density altitude was calculated by the IIC to be about 9,240 feet for the cruise altitude about the time of the accident flight. An examination of the airplane wreckage was conducted by a FAA inspector at the accident site. The airplane's fuselage and wings were observed to have been substantially damaged. All major structural components of the airplane were present in the wreckage. The inspector observed that the engine primer plunger was in the unlocked and extended position. The primer plunger was observed to be undamaged and would appropriately lock when the lugs where engaged. Further, the recently installed spark plugs were removed and observed to be dark in color. No additional anomalies were observed that would preclude normal operation of the engine. The airplane's manual, starting cockpit checklist states to use the primer 2 to 6 strokes and then to lock the primer plunger.