On May 25, 1998, about 1500 eastern daylight time, a Cessna 175, N6577E, was substantially damaged during a forced landing near Pemberton, New Jersey. The certificated private pilot and passenger were not injured. Visual meteorological conditions prevailed and no flight plan was filed for the flight destined for the Philadelphia Seaplane Base (9N2), Essington, Pennsylvania. The personal flight was conducted under 14 CFR Part 91. The pilot reported that prior to his departure from Lake Hinkley, New York, at 1245, he added 20 gallons of fuel, which brought the total fuel onboard between 45 and 48 gallons. He stated that he purchased this fuel at a local airport and transported it to his airplane at the lake, since no fueling services were available at Lake Hinkley. The pilot estimated the flight would take him about 2 1/2 hours to complete. He reported that while en route, the airplane was operating at a decreased power level, requiring him to continually add power to maintain the same RPM amount and "keep it on the step." About 30 minutes from his destination, at 1500, the engine lost power, and the pilot "landed the airplane in a corn field, out of fuel." He stated that he had no mechanical problems with the airplane, and that the fuel gages gradually decreased during the flight, however he "would not rely on the fuel gages in a forty year old airplane." A Federal Aviation Administration Inspector reported that the airplane impacted the field on its water floats, and slid to a stop in an upright position. Both fuel tanks were examined by the Inspector, and found intact and empty. A mechanic, who inspected the airplane after the accident, reported that the magneto oil seals were broken and oil was discovered leaking into both magnetos. Spark plug wires were found "frayed" and "old" and according to the mechanic, their malfunction would have caused an increased fuel consumption by the engine. According to a representative of the engine's manufacturer, the fuel consumption for the model engine was 8 to 10 gallons per hour. The representative also stated that the engine would not consume much more fuel than 10 gallons per hour if the magneto timing was incorrect, oil was leaking inside the magnetos, and their harnesses were in poor condition. The pilot reported 250 hours of total flight experience, 10 hours of which were in the make and model of the accident airplane.