SEA04FA188 · Beech A-36

On the day after the aircraft sat out all night, in what was at times heavy rain, the pilot performed a preflight inspection prior to his departure for a local sightseeing flight. During that preflight he collected fuel from the left wing tank, and that sample revealed about one inch of water in the bottom of the nine inch long fuel sampler. He also found trace amounts of water in the right tank and center drain sump. Although he took a second sample from the left tank that did not show any more water contamination, he did not rock the wings to dislodge any trapped water prior to taking the second sample. Then after starting the engine, he taxied on the uneven undulating grass surface in order to get to the north end of the grass runway. During that taxi, the aircraft's wings rocked gently dislodging additional trapped water. The pilot then initiated his takeoff to the south, and although the aircraft initially accelerated as expected, about one-quarter way down the runway, the engine experienced a partial loss of power. At that point the pilot lowered the aircraft nose, but elected to continue the takeoff roll. After a few seconds the engine accelerated to near full power, and the pilot increased the pitch attitude in an attempt to get the aircraft to climb. But before the aircraft had traveled two-thirds of the way down the runway, the engine starting coughing and missing again, and the pilot aborted the takeoff at or very near the end of the runway. Because he had delayed the abort, he was unable to stop the aircraft prior to it departing the end of the runway, crossing over a paved road, going through a barbed wire fence, and impacting some brush and a parked utility trailer. A post-accident engine inspection and engine run found no evidence of any mechanical failure or malfunction.

Verbatim NTSB analysis and probable cause from the NTSB dataset