On May 12, 2000, at about 1338 eastern daylight time, a Piper PA-18-150, N760WB, registered to Island Aerial Tours Inc., operating as a 14 CFR Part 91 banner tow flight, crashed while maneuvering to pick up a banner. Visual meteorological conditions prevailed and no flight plan was filed. The airplane sustained substantial damage. The commercial pilot sustained serious injury. The flight was originating at the time of the accident. The pilot stated he took off from the grass runway. At about 200 feet he felt a loss of engine power. The tachometer indicated 2,450 rpm and was decreasing. He observed golfers to his front; applied full left rudder and forward stick to maintain airspeed. "After doing this I can not remember anything more until they put me in the ambulance." Witnesses stated they observed the airplane on climbout. The airspeed was described as slow. The airplane was observed to make a steep left turn (45 degrees or more) between 200 to 250 feet. One witness stated, "It was like he stopped in mid air and made a U-turn." The nose of the airplane pitched down, and the airplane collided with terrain. According to the FAA, there were no reports of engine difficulty from any of the witnesses. Examination of the flight control system and engine assembly and accessories revealed no evidence of a precrash mechanical failure or malfunction. (For additional information see FAA Inspector Statement and Textron Lycoming Mishap Investigation Field Notes, attachments to this report.)