Sierra Trigger for Mercury Mariner 4-Cylinder Outboard Motors - 18-99428

The Sierra 18-99428 trigger is an ignition timing component built for Mercury and Mariner 4-cylinder outboard motors. The trigger works as part of the ignition system, sending timing signals to the switch box so spark fires at the correct point in the engine cycle. A trigger that has failed or is reading inconsistently is a common cause of hard starting, engine misfire, rough idle, or a no-spark condition on 4-cylinder Mercury and Mariner outboards. Replacing a worn or damaged trigger with a properly matched unit restores accurate ignition timing and helps the engine run smoothly across the RPM range.

This trigger is sold as a standalone replacement part, letting you address an ignition timing fault without replacing the entire ignition system. It is designed to install in place of the original trigger using the existing mounting points on 4-cylinder Mercury and Mariner powerheads.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-99428
• Product Name: Mercury Mariner Trigger - 4 Cyl.
• Category: Outboard Stator and Trigger
• Engine Configuration: 4-cylinder
• Weight: 0.5 pounds
• UPC: 808282394592

Fitment

• Mercury and Mariner 4-cylinder outboard motors

Frequently Asked Questions

What is the Sierra 18-99428 trigger used for? The Sierra 18-99428 is an ignition trigger that sends timing signals to the switch box on Mercury and Mariner 4-cylinder outboard motors, allowing the ignition system to fire spark at the correct point in the engine cycle.

Which engines does the 18-99428 trigger fit? This trigger is designed for Mercury and Mariner 4-cylinder outboard motors.

What are signs that a trigger needs to be replaced? Hard starting, misfiring, rough idle, and no-spark conditions on a 4-cylinder Mercury or Mariner outboard can point to a failed or failing trigger such as the 18-99428.

How much does the 18-99428 trigger weigh? The Sierra 18-99428 trigger weighs 0.5 pounds.

Is the 18-99428 an OEM or aftermarket part? The 18-99428 is a Sierra-branded replacement trigger manufactured to work as an ignition component on 4-cylinder Mercury and Mariner outboards.

Does the 18-99428 replace the entire ignition system? No, the 18-99428 is a standalone trigger component, letting you replace just the failed timing trigger rather than the full ignition system.

What is included when ordering part 18-99428? Ordering the Sierra 18-99428 includes the trigger unit itself for installation on a 4-cylinder Mercury or Mariner outboard.

Can the 18-99428 trigger be used on non-Mercury outboards? The 18-99428 is built specifically for Mercury and Mariner 4-cylinder outboard motors.

What UPC is associated with the Sierra 18-99428 trigger? The Sierra 18-99428 trigger carries UPC 808282394592.