On July 29, 1994, at 1450 central daylight time (CDT), a Piper PA-32-300, N8144Y, registered to Ardis M. Luthe of Marshalltown, Iowa, and piloted by a commercially certificated pilot, was substantially damaged during a collision with the ground following an off airport landing. Visual meteorological conditions prevailed at the time of the accident. The 14 CFR Part 91 flight was not operating on a flight plan. The pilot and passenger reported no injuries. The flight departed Marshalltown, Iowa, at 1445 CDT. According to the pilot's written statement on NTSB Form 6120.1/2, the airplane experienced a partial power loss shortly after takeoff. The pilot said the airplane was about 200 feet above the ground when she first noticed the power loss. The pilot said she leveled the airplane off when she observed the airspeed decreasing. Once leveled off, the airplane accelerated to its previous climb speed of 80 knots. The pilot said, "The level attitude....seemed to stabilize everything... ." She said she decided to turn toward the cross runway and land. According to the pilot, about halfway through the turn the airplane's engine power "...seemed to diminish further... ." Faced with a diminishing power situation, the pilot "established a gliding attitude. With altitude decreasing, I selected a grassy strip between a cornfield and the ditch along highway 233 for an emergency landing." She said that "Shortly after touch down the right main gear dropped into a grass filled waterway washout hole near the edge of the ditch and broke off." Shortly after this event the airplane slid to a stop. The on-scene investigation revealed engine control continuity, fuel samples that were not contaminated, and an electric fuel pump that pumped fuel to the engine's fuel injector nozzles. Magnetos created spark when turned, the air filter was free of debris, the air inlet housing was clear of any obstructions, all cylinders had compression when given the thumb compression check. Spark plugs were free of debris by the electrodes and were a tan/gray color. Engine gear train continuity was established when the engine was turned by hand. No oil leaks were observed on the engine or within its compartment. The engine's fuel servo was flow checked at a full power setting. The manufacturer's test specification states the limits are between 156.8 and 163.2 pounds per hour (pph). The flow test showed 163.5 pph. The manufacturer's idle setting limits were between 9.0 and 11.0 pph, the test resulted in 9.5 pph. The unit's finger screen was free of any contaminants. The flow divider's outflow openings showed consistent fuel pressure at each of its six openings. The unit's fuel pressure line outlet had fuel flow output. The engine driven fuel pump was examined and functioned according to the manufacturer's specifications. The cylinder fuel injector nozzles tested at pressures ranging between 32.7 and 34.0 pph. The left magneto's drive side bearing was loose in the housing. When checked on the test stand the magneto produced spark from an engine idle to full power setting. The right magneto produced the same type spark within the previously stated power range. Both magnetos were able to be grounded out.