On March 15, 2018, about 1335 eastern daylight time, a privately owned and operated Cessna 177, N713CX, was substantially damaged during a forced landing, following a partial loss of engine power during initial climb from Key West International Airport (EYW), Key West, Florida. The airline transport pilot incurred minor injuries and the two passengers were not injured. The personal flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no flight plan was filed for the planned local flight that was originating at the time of the accident.The airline transport pilot reported that his friend, the front-seat passenger, had recently purchased the airplane, but he only held a student pilot certificate and did not possess a logbook endorsement to fly that make and model airplane solo. The airline transport pilot intended to go on a short sightseeing flight with the two passengers. The preflight inspection, engine start, taxi, and engine run-up were uneventful. During initial climb from runway 9, about 400 ft above ground level, the engine power suddenly reduced to idle. The airline transport pilot lowered the nose and made a shallow left turn to avoid trees and reach shallow water; however, the airplane contacted powerlines and came to rest upright in a parking lot, prior to reaching the shallow water. Initial examination of the wreckage by a Federal Aviation Administration (FAA) inspector revealed that both wings and the fuselage sustained substantial damage. The inspector noted that adequate fuel remained onboard and fuel had leaked from the airplane after impact. He confirmed mixture and throttle control continuity. He also confirmed that the fuel selector was positioned to both. Due to the disposition of the wreckage, the inspector was not able to rotate the propeller and planned to further examine the engine after it was recovered. The wreckage was examined again by an FAA inspector and a National Transportation Safety Board investigator at a recovery facility. The engine remained intact and attached to its mounts; however, the mounts and firewall were impact separated from the fuselage. The accessories on the rear of the engine exhibited some damage from contact with the firewall during impact. The engine driven fuel pump exhibited an impact hole in the bottom side. One propeller blade was bent aft about midspan and both blades exhibited damage consistent with wire strikes. The top spark plugs were removed for examination and access to the cylinders for a lighted borescope. The spark plug electrodes were intact and light gray in color. When the propeller was rotated by hand, thumb compression was established to all cylinders. Valve train continuity was established to the rear accessory section of the engine. Both magnetos were removed and produced spark at all leads when rotated by an electric drill. The air filter was removed and examined. The air flow ducts to the fuel servo were clear and unobstructed. The fuel flow divider was disassembled and noted to be absent of any debris. The diaphragm was intact and did not exhibited any damage. When the fuel sump was disassembled, its fuel screen was observed to be dry and absent of debris. The fuel sump bowl contained a small amount of gel at the bottom. The fuel screen was removed from the fuel servo. The screen exhibited some rust on the screen and in the servo, consistent with the airplane sitting unused over a period of time. The examination of the engine did not reveal any preimpact mechanical malfunctions. The four-seat, high-wing, fixed-tricycle-gear airplane was manufactured in 1968 and powered by a Lycoming IO-360, 200-horsepower engine, equipped with a two-blade, fixed-pitch, Hartzell propeller. Review of FAA records revealed that the student pilot purchased the airplane on October 16, 2017. Review of the airplane's maintenance records revealed that the most recent annual inspection was completed on February 1, 2018. At that time, the airframe had accumulated about 3,602 total hours of operation and the engine had accumulated 1,771 hours since major overhaul. The airplane had flown about 2 hours from the time of the most recent annual inspection, until the accident. The recorded weather at EYW, at 1253, was: wind from 030° at 14 knots; visibility 10 statute miles; clear sky; temperature 19° C; dew point 9° C; altimeter 30.17 inches of mercury.