Sierra 18-99396 Ignition Trigger for Mercury/Mariner 3-Cylinder 30-90 HP Outboards, Replaces 855746A12

The Sierra 18-99396 is an ignition trigger built for Mercury/Mariner 3-cylinder outboards, replacing the factory trigger that signals the ignition system with crankshaft position for correct spark timing. It is a flange-mount component with a digital output type and a measuring range of 500 to 3000 RPM, rated to withstand temperatures up to 250 degrees Fahrenheit, making it suited to the heat and vibration found inside an outboard powerhead.

This trigger fits Mercury/Mariner 3-cylinder outboards rated 30, 40, 50, 55, 65, 75 and 90 HP from 1996-2007, and is a direct replacement for the factory trigger assembly on these engines. It ships as a single unit ready to install in place of a worn or failed OEM trigger, restoring reliable ignition timing signal to the powerhead.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-99396
• Fits: Mercury/Mariner 3-cylinder outboards, 1996-2007
• Horsepower Range: 30, 40, 50, 55, 65, 75 and 90 HP
• Measuring Range: 500 to 3000 RPM
• Mounting Type: Flange mount
• Output Type: Digital
• Upper Temperature Rating: 250 degrees Fahrenheit
• Dimensions: 6 x 6 x 1.75 inches
• Weight: 0.6 pounds
• UPC: 808282394295

Fitment

• Mercury/Mariner 3-cylinder outboards, 1996-2007: 30, 40, 50, 55, 65, 75 and 90 HP

Replaces (OEM)

• 855746A12
• 855746A1
• 854512T
• 834520T

Frequently Asked Questions

What does the Sierra 18-99396 trigger fit? The Sierra 18-99396 fits Mercury/Mariner 3-cylinder outboards rated 30, 40, 50, 55, 65, 75 and 90 HP built from 1996-2007.

What OEM part numbers does this trigger replace? Sierra 18-99396 replaces OEM Mercury/Mariner numbers 855746A12, 855746A1, 854512T, and 834520T.

Is the 18-99396 a direct OEM replacement or will I need to modify anything? Yes, the Sierra 18-99396 is a direct replacement for the listed OEM triggers on compatible 3-cylinder Mercury/Mariner outboards, with no modification required.

How much does this trigger weigh? The Sierra 18-99396 ignition trigger weighs 0.6 pounds.

What are the physical dimensions of the 18-99396 trigger? This trigger measures 6 x 6 x 1.75 inches.

How is the trigger mounted on the engine? The 18-99396 uses a flange mount for installation on compatible Mercury/Mariner 3-cylinder powerheads.

What is the operating RPM range of this trigger? Sierra 18-99396 has a measuring range of 500 to 3000 RPM.

What output type does the trigger use? The 18-99396 uses a digital output type to signal the ignition system.

What temperature can this trigger withstand? It is rated for operation up to 250 degrees Fahrenheit, suited to conditions inside a running outboard powerhead.

Does this trigger include mounting hardware or other components? The Sierra 18-99396 ships as the trigger assembly itself; check your engine's service manual for any hardware reused from the original trigger during installation.

Will this work on a 4-cylinder Mercury outboard? No, the Sierra 18-99396 is built specifically for 3-cylinder Mercury/Mariner outboards in the 30-90 HP range, not 4-cylinder models.

Can I use 18-99396 if my engine trigger part number is 855746A12? Yes, the Sierra 18-99396 directly replaces OEM number 855746A12 along with 855746A1, 854512T, and 834520T.