On May 31, 2022, at 0940 Pacific daylight time, a Vans RV-8, N298DM, sustained substantial damage when it was involved in an accident near Galice, Oregon. The pilot and passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot completed a 20-minute flight and landed in Grants Pass, Oregon, with the intention of picking up his spouse. The airplane started normally and they departed from runway 31 about 0930. The pilot continued to the west until reaching the Rouge River, where he maneuvered over the river about 3,000 feet above mean sea level (msl) with the engine operating at 2,200 rpm. After a few minutes, the pilot heard a “pop” emanating from the engine compartment followed by a loss of engine power. The pilot added full throttle, verified the mixture was full rich, cycled the magnetos, and switched the fuel selector position to the other tank. Despite the pilot’s troubleshooting attempts, the engine did not restart. The pilot looked for a location to perform an emergency landing and noted that the airplane was too high to align with the gravel bars in the immediate vicinity. With no suitable terrain ahead, he opted to ditch in the river adjacent to the shoreline. The airplane touched down in a calm current near some exposed rocks. The airplane settled on rocks and the pilot and passenger sat on the canopy for about 15 minutes. A team of swift-water rescue divers arrived at a boat ramp across the river with the intention of performing a training exercise that morning. The team carried the pilot and passenger to shore without injury. During the accident sequence, the left wing was substantially damaged. The pilot estimated that there was about 30 gallons of fuel onboard the airplane at the time of the accident. The engine was overhauled prior to being installed on the airplane. The airplane and overhauled engine had amassed 98.9 flight hours before the accident. A Federal Aviation Administration certified Airframe and Powerplant Mechanic examined the wreckage. He stated that upon rotation of the propeller, the rocker arms on the intake and exhaust valves did not move. Removal of the accessory gear housing revealed that the crankshaft gear was missing its retaining bolt and lock-plate (see Figure 1 below). After removing the gear, he noted the alignment dowel was sheared off and the crankshaft gear’s mounting flange was damaged. He removed the oil sump and found debris consistent with the mounting flange material but was unable to locate the missing bolt. Figure 1: Accessory Housing Removed (pictures provided by mechanic)