Sierra 18-99403 Trigger Assembly for Mercury 4-Cylinder Outboards

The Sierra 18-99403 is a replacement trigger assembly designed specifically for Mercury 4-cylinder outboard engines featuring a hooked arm configuration. This critical ignition system component works in conjunction with the stator to generate the timing signal that controls spark delivery to the engine.

Key Features:

• Direct replacement for Mercury Marine OEM trigger assemblies
• Hooked arm design for 4-cylinder Mercury outboard applications
• Precision-manufactured to ensure accurate timing signal generation
• Durable construction for reliable performance in marine environments
• Sierra quality engineering for dependable ignition system operation

This trigger assembly is an essential component for maintaining proper ignition timing and engine performance. Sierra Marine parts are manufactured to meet or exceed OEM specifications, providing a cost-effective alternative to factory parts while ensuring reliable operation.