Mercury - Exhaust Elbow Gasket Standard Cooling Series Composite Marine Seal 99777Q02. Overview. When you spend enough time on the water, you learn to appreciate the parts that quietly keep everything running right. The pieces you never think about until the day they fail-and the ones that earn your trust by never letting you down. That's exactly how the 99777Q02 Exhaust Elbow Gasket feels: steady, dependable, and built for the kind of long days when the engine hum becomes its own kind of comfor