On July 26, 1998, about 1400 central daylight time, a Piper PA-25-235, N8807L, registered to Aerial Ads of the Southeast, collided with trees during a forced landing on a golf course near Panama City Beach, Florida. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 CFR Part 91 banner tow flight. The airplane was substantially damaged and the commercial-rated pilot, the sole occupant, was seriously injured. The flight originated about 1 hour 30 minutes earlier. The pilot stated that during the second banner tow flight of the day while flying at 800 feet msl over the beach, the engine sputtered then quit. He initiated a descent for a forced landing during which the engine responded momentarily then quit again. He maneuvered the airplane towards a golf course fairway due to congestion on a nearby road and dropped the banner. After touchdown on the fairway during the landing roll, the left wing collided with a tree causing the airplane to yaw to the left 180 degrees. The airplane then became airborne momentarily, collided with a tree about 15 feet agl, and came to rest in a nose low attitude resting against the downslope of an embankment to a pond. According to the individual who assisted with the recovery of the airplane, the fuel tank was not damaged and did not contain any fuel. Also, no fuel was found in the fuel gascolator and the carburetor was separated due to impact damage. No fuel was noted on the water adjacent to the resting point of the airplane. According to the operator, after recovery of the airplane, the fuel tank was filled with water then drained 5 gallons at a time. The fuel gauge was determined to move with each decrease in fuel quantity. The fuel tank was also removed from the airplane and inspected internally with no defects noted.