On June 26, 1998, at 1700 eastern daylight time, a homebuilt, Fisher FP 404, N6188X, was substantially damaged when it collided with terrain during a forced landing near Louisa, Virginia. The certificated private pilot received minor injuries. Visual meteorological conditions prevailed and a flight plan was not filed. The personal flight was conducted under 14 CFR Part 91. The flight originated at Warrenton, Virginia, and was destined for Louisa, Virginia. According to the pilot, he was cruising at 1,500 feet MSL, en route to Louisa to purchase fuel, when the engine RPM dropped from 5,800 to 3,000. The pilot said he, "played with the throttle," but was unable to maintain altitude, and elected to perform a forced landing to a field. During the landing, the airplane exited the field, crossed a fence, and impacted on State Route 68. The airplane was moved to a hangar where a Federal Aviation Administration (FAA) Inspector examined the wreckage. According to the Inspector, the uncertificated two cycle engine was rotated manually, and it was lubricated. Examination of the fuel in the gascolator revealed no water or contaminants. The examination did not reveal any anomalies with the airplane or the engine. The pilot reported over 190 hours of total flight experience including 12 hours in make and model. He said the total capacity of the fuel tank was 7 1/2 gallons, and the fuel burn was 5 gallons per hour. He said he was airborne less than an hour, and he should have had at least 2 to 2 1/2 gallons of fuel remaining.