The airplane had been fueled and then flown for about three hours and fifteen minutes prior to landing at a private landing strip. The pilot then departed from the private strip and was enroute to a nearby airport when the engine experienced a total loss of power. The pilot performed a forced landing into a reservoir, which resulted in substantial damage to the ailerons. The airplane came to rest upright and floated for several minutes, while the pilot egressed and was rescued by a local resident. After the airplane was recovered from the reservoir, about 20 gallons of fuel was drained from the right wing fuel tank. The left wing fuel tank was void of fuel and the fuel selector was selected to the left tank. Examination by a Federal Aviation Administration inspector revealed no other anomalies that would have precluded normal engine operation.