On September 12, 1993, about 1800 central daylight time, a Boeing A75N1 airplane, N54941, experienced loss of engine power during cruise and landed off-airport near Springfield, Missouri. The airline transport pilot and passenger incurred serious injury, and the airplane was substantially damaged in the forced landing. Visual meteorological conditions existed in the area. The personal flight originated in Hannibal, Missouri, about 1515 without a flight plan, and operated under 14 CFR 91. According to the pilot's statement, approximately 45 minutes into the flight after refueling, the engine quit. He then initiated a forced landing. The airplane landed in a "flat" attitude on soft, rough terrain. The airplane was examined by an airframe and powerplant mechanic shortly after the accident. The mechanic reported finding the primer supply line disconnected at the fuel strainer. Examination of the line showed the flared end of the primer line had slipped out from the coupling nut and sleeve due to shrinkage of the flare.