Narrative:

While transiting northbound approximately 200-250 yards off the coast (waterline); I experienced a slow loss of engine power. Turned toward isolated stretch of beach and prepared for a precautionary landing to the south as wind was from that direction. Throttle was wide open with about 1/3 power. I initially thought the cause could be carb ice. Very shortly after wheels touched power increased to what seemed to be full power. Lifted off and made a turn; approximate 30 degree; toward north and about two thirds of the way into turn the power reduced again. Turned back toward beach again and another precautionary landing. As wheels touched; aircraft bounced hard twice. Power was restored after approximately 3 second of rolling on mains; tailwheel never touched. Power seemed to be fully restored. I quickly deduced that there must be a partial fuel blockage. I pulled up straight ahead and climbed to approximately 500 ft to make a very gentle turn to the right toward a nearby airport. I was able to climb to approximately 800 ft but had two more episodes of slow engine power loss during this phase. A violent back and forth rocking of wings seemed to help clear the engine and power was at least partially restored. After arriving at the airport and checking all possible causes; the fuel tank was drained of remaining fuel; the line and valve were removed from the bottom of the fuel tank. The strainer in the tank was found to have a small amount of water and was partially plugged with a trash and a flaky substance. Parts were cleaned and reinstalled.

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Original NASA ASRS Text

Title: A J3 Cub lost power at about 800 FT just off the coast; so the pilot attempted a beach landing. Upon touchdown power was restored; (happened twice) so he maneuver vigorously to clear a fuel line; then flew to nearby airport where water and debris were discovered in the fuel tank.

Narrative: While transiting northbound approximately 200-250 yards off the coast (waterline); I experienced a slow loss of engine power. Turned toward isolated stretch of beach and prepared for a precautionary landing to the south as wind was from that direction. Throttle was wide open with about 1/3 power. I initially thought the cause could be carb ice. Very shortly after wheels touched power increased to what seemed to be full power. Lifted off and made a turn; approximate 30 degree; toward north and about two thirds of the way into turn the power reduced again. Turned back toward beach again and another precautionary landing. As wheels touched; aircraft bounced hard twice. Power was restored after approximately 3 second of rolling on mains; tailwheel never touched. Power seemed to be fully restored. I quickly deduced that there must be a partial fuel blockage. I pulled up straight ahead and climbed to approximately 500 FT to make a very gentle turn to the right toward a nearby airport. I was able to climb to approximately 800 FT but had two more episodes of slow engine power loss during this phase. A violent back and forth rocking of wings seemed to help clear the engine and power was at least partially restored. After arriving at the airport and checking all possible causes; the fuel tank was drained of remaining fuel; the line and valve were removed from the bottom of the fuel tank. The strainer in the tank was found to have a small amount of water and was partially plugged with a trash and a flaky substance. Parts were cleaned and reinstalled.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.