Mercury - Exhaust Elbow Gasket Dry Joint Full Flow Marine Composite 864547A02. Overview. Every boater knows that a smooth-running engine is more than just horsepower and throttle response-it's about trust. Trust that when you fire up your MerCruiser, everything inside is sealed, aligned, and ready to take you wherever the day leads. The Mercury Marine 864547A02 Exhaust Elbow Gasket is one of those small, quiet heroes that keeps your exhaust system breathing cleanly and your outings free from sur