On July 16, 2000, about 1630 Eastern Daylight Time, a homebuilt Surrel Guppy, N4425W, was substantially damaged after it experienced a loss of engine power during the initial climb after takeoff from the Harford County Airport (OW3), Churchville, Maryland. The certificated private pilot was seriously injured. Visual meteorological conditions prevailed and no flight plan had been filed for the local flight conducted under 14 CFR Part 91. The airplane departed Runway 01, a 1,600 foot-long, turf runway. The pilot stated that after a normal acceleration and lift off, he noticed the engine tachometer indicated 2,900 rpm, instead of the normal 3,450 rpm. Additionally, the corner of the airplane's canopy became dislodged. The pilot was unable to secure the canopy and felt he would have "no problem making a gentle left turn to land on a parallel runway;" however, during the turn, about 50 feet above the ground, he became "distracted and stalled" the airplane about 300 feet short of the runway. Examination of the airplane was conducted by a Federal Aviation Administration inspector. The airplane was equipped with a 4-cycle Kohler, model CH25S lawn mower engine. A hole was found in the right cylinder rocker box cover, and "some debris and filings" were observed on the right cylinder exhaust valve.