Sierra 18-99393 Ignition Trigger for Mercury/Mariner 3-Cylinder Outboards, 1987-1999, 45-90 HP, Replaces 99021A15

The Sierra 18-99393 Ignition Trigger is a direct replacement trigger component for Mercury and Mariner 3-cylinder outboard engines built from 1987 to 1999. The trigger is a key part of the ignition system, working with the stator and switch box to generate the timing signal that fires the spark at the correct point in the engine cycle. A worn or failed trigger commonly causes hard starting, misfiring, poor idle, or a no-spark condition, making this a frequent replacement item for outboard owners maintaining or troubleshooting their ignition system.

This trigger is designed for Mercury/Mariner 3-cylinder powerheads covering the 45 JET, 50, 60, 65, 70, 75, 80, and 90 HP range within the stated model years. It measures 7.1 x 6.3 x 1.9 inches and has a black finish. Because it cross-references to several original Mercury/Mariner part numbers, it can be used to replace any of those numbers on qualifying 3-cylinder powerheads, giving owners and technicians a straightforward way to confirm fitment when servicing the ignition system.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-99393
• Category: Mercury Outboard Stators & Triggers
• Color: Black
• Dimensions: 7.1 x 6.3 x 1.9 inches
• Weight: 0.6 pounds
• UPC: 808282394264
• OEM Cross Reference: 99021A15, 99021A16, 99021A13, 99021A8, 99021A3, 99021A5
• Fitment: Mercury/Mariner 3-cylinder outboards, 1987-1999, 45 JET, 50, 60, 65, 70, 75, 80, 90 HP

Fitment

• Mercury/Mariner 3-cylinder outboards, 1987-1999
• 45 JET, 50, 60, 65, 70, 75, 80, and 90 HP

Replaces (OEM)

• 99021A15
• 99021A16
• 99021A13
• 99021A8
• 99021A3
• 99021A5

Frequently Asked Questions

What engines does the Sierra 18-99393 trigger fit? It fits Mercury/Mariner 3-cylinder outboards built from 1987 to 1999, covering the 45 JET, 50, 60, 65, 70, 75, 80, and 90 HP models.

What OEM part numbers does this trigger replace? The Sierra 18-99393 cross-references to OEM numbers 99021A15, 99021A16, 99021A13, 99021A8, 99021A3, and 99021A5, so it can be used in place of any of those on a qualifying 3-cylinder powerhead.

What color is the Sierra 18-99393 trigger? The trigger has a black finish.

What are the dimensions of this trigger? The Sierra 18-99393 measures 7.1 x 6.3 x 1.9 inches.

How much does the Sierra 18-99393 trigger weigh? It weighs 0.6 pounds.

What symptoms indicate a failing ignition trigger? Hard starting, misfiring, a rough or unstable idle, and a no-spark condition are common symptoms of a failing trigger on Mercury/Mariner 3-cylinder outboards, and the Sierra 18-99393 is a direct replacement for these issues.

Does this trigger fit 2-cylinder or 4-cylinder Mercury outboards? No, the Sierra 18-99393 is designed specifically for Mercury/Mariner 3-cylinder outboard engines within the 1987-1999 range.

Is the Sierra 18-99393 trigger compatible with the 45 JET model? Yes, the 45 JET is one of the engines covered by the Sierra 18-99393, along with the 50, 60, 65, 70, 75, 80, and 90 HP 3-cylinder models.

What does an ignition trigger do in an outboard motor? The trigger works with the stator and switch box to generate the timing signal that tells the ignition system when to fire the spark, and the Sierra 18-99393 provides this function for Mercury/Mariner 3-cylinder outboards.

What is the UPC for the Sierra 18-99393 trigger? The UPC for the Sierra 18-99393 Mercury/Mariner 3-cylinder trigger is 808282394264.

Can I use this trigger to replace multiple different Mercury part numbers? Yes, because the Sierra 18-99393 cross-references six different OEM numbers (99021A15, 99021A16, 99021A13, 99021A8, 99021A3, 99021A5), it works as a replacement for any engine originally equipped with one of those parts.

What year range of Mercury/Mariner outboards does this trigger cover? The Sierra 18-99393 covers Mercury/Mariner 3-cylinder outboards built between 1987 and 1999.