- Function and benefit: CDI ignition control unit for Mercury marine outboard motors delivers faster response and higher spark energy, producing a stronger ignition and precise timing under all operating conditions to improve engine efficiency. - Compatibility and specifications: 332-7778, 332-7778A12, 332-7778A9 CDI switch boxes for Mercury outboards from 50 to 275 horsepower with 3- and 6-cylinder configurations. - Performance consistency: capacitor discharge characteristics ensure a stable and consistent high-voltage pulse for reliable starts and smooth running. - Replacement guidance: if the engine shows starting difficulties, weak acceleration, or occasional stalling, replace promptly to maintain safe operation. - Use scenarios: 1) Replace worn CDI box on a Mercury 3- or 6-cylinder outboard to restore reliable starting and steady acceleration. 2) Upgrade an aging Mercury 50-275 hp motor to improve throttle response during open-water boating. 3) Use in marine maintenance to ensure consistent ignition energy across multiple engines in a fleet.