On July 6, 1994, about 1140 central daylight time, a Beech Baron 58, N625P, was substantially damaged when it struck trees on approach to land at Kings Land O'Lakes Airport, Land O'Lakes, Wisconsin. The pilot received minor injuries. The 14 CFR Part 91 flight originated in Timmerman, Wisconsin, on an IFR flight plan which was cancelled prior to the initiation of the approach. The flight operated in visual meteorological conditions. According to the pilot's statement, after departing Timmerman he realized that the tachometer for the left propeller was not operating. He found that he was able to keep the left and right propellers in synchronization at either full or cruise power, so he decided to continue the flight. As he began his approach to land at Kings Land O'Lakes Airport, he again experienced the synchronization problem when he reduced the power. While on final approach, he became preoccupied with the problem and impacted trees.