The pilot of the experimental amateur built airplane reported that, after descending to a local river, he increased the throttle to add power and level off, but the engine did not respond. The engine lost total power, and he attempted an in-flight engine restart to no avail. The pilot initiated a landing to a nearby island in the river, however, during the landing, the airplane’s airspeed was fast, and braking was ineffective. The pilot turned the airplane to the right toward vegetation and subsequently impacted a sandbank. The airplane sustained substantial damage to the left-wing and the empennage. A postaccident examination of the throttle control linkage revealed that the throttle control had separated at the throttle control pivot arm. The bolt, washer and nut which secured the cable to the throttle control pivot arm had backed out and were not located during the examination. Additionally, a bolt, bushing binding and nut were used to secure the throttle control pivot arm to a cross-member located between the throttle control cable and the carburetor cable binding. The return spring is designed to open the throttle to the fully open throttle position when the throttle control malfunctions. The torque on the nut that secured the pivot arm to the cross-member was excessive and consequently prevented the pivot arm from allowing the return spring to open the throttle.