Event Summary
A solo cross-country flight was disrupted when the pilot experienced throttle control difficulties. According to the pilot's statement, the throttle had become stuck several times during the enroute phase. While approaching Ft. Myers, the pilot retarded the throttle but was subsequently unable to advance it. Unable to maintain altitude, the pilot executed a forced landing.
Investigation Findings
Post-flight examination of the aircraft revealed that all engine controls were free to move and had full travel in both directions. The friction knob on the throttle was found screwed completely out, but this did not hamper full use of the throttle. The throttle control mount nut was secured to the instrument panel and was not loose.
However, the throttle linkage at the carburetor was incorrectly installed. The linkage was hooked up at the top mount hole, which resulted in the throttle control having only about 1-5/8 inches of full travel from idle to full power. This contrasts with the 3 inches or better of travel typical in other Cessna 172 installations. The limited travel would cause rapid power changes with only small movements of the throttle control.