On December 28, 1996, about 1635 eastern standard time, an Issoire Siren Pik-30, N25RJ, registered to a private owner, was damaged during a forced landing near Boynton Beach, Florida, while on a Title 14 CFR Part 91 personal flight. Visual meteorological conditions prevailed at the time and no flight plan was filed. The aircraft received substantial damage and the commercial-rated pilot was not injured. The flight originated from the Willis Glider Strip, the same day, about 1315. The pilot stated that after departure from Willis Gliderport he flew west where he shut down the engine and began to glide. He was gliding with another aircraft. About 3 hours later he turned back to the gliderport. There were no thermals and as the glider descended through 1,000 feet, he tried to start the engine, using the starter, to motor home. The engine would not start using the starter and he attempted to dive the aircraft for an airstart. The engine still would not start and he ran out of altitude and had to make a forced landing in the swamp. On landing the aircraft ground looped and the tail broke off. The pilot of the other aircraft called for rescue. The pilot was rescued 45 minutes later. The pilot stated that 5 days after the accident, after the aircraft was recovered from the swamp, he started the engine. The engine ran but would not develop full power. Two days later he changed the fuel filter, and the engine started and ran to full power with no evidence of failure or malfunction. He stated he is not sure the fuel filter prevented the engine from starting for the engine was running fine when he did the normal shutdown to glide. He stated he is not sure he turned on the electrical power to the engine before trying to start it with the starter and does not remember if it turned over with the starter. He also does not know if he attained enough airspeed in the dive to get the engine to start.