On February 22, 1998, about 1424 eastern standard time, a Cessna 150A, N757NK, registered to Island City Flying Service, operating as a 14 CFR Part 91 fish spotting flight, experienced a total loss of engine power in cruise flight, and made a forced landing in the Gulf of Mexico, about 10 miles southwest of Key West, Florida. Visual meteorological conditions prevailed and a VFR flight plan was filed. The airplane was not recovered and is presumed to be destroyed. The commercial pilot reported no injuries. The flight originated from Key West, about 3 hours 49 minutes before the accident. The pilot said, "he thought that fuel would not be a problem due to the airplane having extended range fuel tanks which held 40 total gallons and burned 6 gallons per hour...I did a normal preflight inspection including, draining fuel sumps and visually checking the fuel...." He also stated, " I flew one hour in level flight, after finding fish, I started a left turn in which I remained in for about two and a half hours waiting for my boat to arrive, when I began to experience a power loss so I began checking switches, magnetos and the fuel selector, and I began to rock the wings." The pilot further stated, "I should have had two and a half to three hours of fuel remaining, and had been advised by the mechanic/instructor not to always trust the fuel gages as they are not very dependable." He said he ran the airplane at 2,000 RPM's to try to extend the fuel burn while he was circling a fishing boat 35 miles offshore at 4,000 feet trying to spot fish, the engine stopped, and he started to descend. As he was passing through 2,500 feet the engine started, and he elected to return to land. He was about 15 miles from Key West when again the engine failed. He made a forced landing next to a lobster boat in the Gulf of Mexico. According to the pilot, "...the aircraft was full of fuel at the time of takeoff...." According to the pilots operating handbook for the Cessna 150A, the aircraft holds 35 gallons of usable fuel and burns 6 gallons an hour, which would have given him approximately 5 hours and 45 of fuel on board. The airplane was not recovered from the water, and no determination could be made on the reason for the loss of engine power.