The pilot, who did not hold an airframe and powerplant (A&P) certificate, stated that after he installed the overhauled engine onto the agricultural airplane, he planned on flying the airplane during the accident flight to break the engine in prior to having it inspected and signed off by an A&P mechanic with inspection authorization. There was no record of a current annual inspection of the airplane prior to the flight. The pilot loaded the airplane with 20 gallons of water to test the spray system since he planned on flying for about an hour. During climb after takeoff, the pilot lost control, and the airplane descended and impacted terrain resulting in substantial damage to both wings and fuselage. The pilot stated there was no mechanical malfunction/failure of the airplane that would have precluded normal operation.