The pilot stated that during the attempted takeoff of an aerial application flight, the engine power seemed low. He continued the takeoff and then realized that the airplane would not remain airborne so he pulled the dump handle releasing about 40 gallons of the 150 gallon load. When the airplane became airborne, about 300 feet before the departure end of the runway, it experienced a total loss of engine power. The pilot lowered the nose and the airplane impacted the runway's overrun area and nosing over. It came to rest inverted about 300 feet past the departure end of the runway. The airplane sustained substantial damage, which included structural damage to both wings and the fuselage. The pilot was uninjured. Examination of the airplane by the Federal Aviation Administration revealed two cylinders that were unable to produce compression and an inoperative magneto. No other anomalies were found.