On June 30, 2013, about 1324 eastern daylight time, an amateur-built Youngster airplane, N258RV, impacted terrain near Grand Haven, Michigan. The pilot sustained serious injuries, and the airplane was substantially damaged. The airplane was registered to and operated by a private individual as a 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed for the flight, which was not operated on a flight plan. The flight originated from the Grand Haven Memorial Airpark just before the accident occurred. The pilot reported that he was performing the initial test flight of the owner's new amateur-built airplane. He performed several fast taxi operations in which the tail of the conventional gear (tail wheel-equipped) airplane was raised and held off the ground for the length of the runway. During the fast taxi operations the pilot did not notice any engine or aircraft control problems. The pilot said he then taxied the airplane to where the owner was at, and had a short discussion where it was decided the pilot would take off and fly the airplane around the traffic pattern and land. The pilot taxied to the runway, performed a run-up check of the engine, proceeded onto the runway, and advanced the throttle for takeoff. He said that the engine accelerated smoothly and he noticed no problems. He rotated about 50 mph and the airplane became airborne. He noticed that the airplane "felt slow" and that it did not seem to be accelerating as it should. The pilot adjusted the control stick for the best rate of climb airspeed and noticed the airspeed decreased quickly with only a small change in the airplane's pitch attitude. At that point, the pilot felt he did not have sufficient runway remaining to safely land the airplane, so he continued the flight. There were power lines off the departure end of the runway, which the pilot was able to clear. He attempted to bank the airplane, but after turning only a few degrees he knew he didn't have the altitude or airspeed to complete the turn, so he leveled the airplane. He determined that the airplane's engine was losing power and verified that the choke and carburetor heat were off. The airplane's engine continued to lose power until the pilot could no longer safely maintain altitude. He attempted to maneuver the airplane to a suitable landing area; however, the airplane stuck trees and subsequently impacted the ground, where it came to a stop. At 1255, the recorded weather conditions at the Muskegon County Airport (MKG), Muskegon, Michigan, about 8 miles north of the accident site were: wind 30 degrees at 6 knots; 10 statute miles visibility; broken clouds at 8,500 ft agl, broken clouds at 13,000 ft agl; temperature 24 degrees C; dew point 13 degree C; altimeter setting 29.91 inches of mercury. The temperature and dew point at the time of the accident were in the range for susceptibility to moderate carburetor icing at cruise power and serious icing at descent power settings. The pilot said that he did not use carburetor heat because when he was trained he was told that the use of carburetor heat reduces engine power.