Sierra CDM Trigger 18-99397 for Mercury/Mariner 6 Cylinder Outboards, Replaces 96455A18 96455T18

The Sierra 18-99397 is a CDM trigger built for Mercury and Mariner 6 cylinder outboard engines. The trigger is a key component of the ignition system, signaling the CDM (Capacitor Discharge Module) to fire the spark at the correct point in the engine cycle. A worn or failing trigger commonly causes misfiring, hard starting, rough idle, or a no-spark condition on one or more cylinders, and replacing it with a properly matched unit restores consistent ignition timing across all six cylinders.

This trigger is designed as a direct fit for Mercury/Mariner 6 cylinder outboards covering the 135, 140, 150, 175, 200, and 240 HP SportJet models from 2000 to 2007. It corresponds to the OEM part numbers 96455A18 and 96455T18, making it straightforward to identify as the correct replacement when cross-referencing against the original Mercury/Mariner part on the engine. It measures 6 x 6 x 1.75 inches and weighs 0.4 pounds, in line with the compact triggers used in these outboard ignition systems.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-99397
• Product Type: CDM Trigger
• Engine Fitment: Mercury/Mariner 6 Cylinder
• HP Fitment: 135, 140, 150, 175, 200, 240 HP SportJet
• Model Years: 2000-2007
• Weight: 0.4 pounds
• Product Dimensions: 6 x 6 x 1.75 inches
• OEM Cross-Reference: 96455A18, 96455T18

Fitment

• Mercury/Mariner 6 cylinder outboards: 135, 140, 150, 175, 200, and 240 HP SportJet, 2000-2007

Replaces (OEM)

• 96455A18
• 96455T18

Frequently Asked Questions

What engines does the Sierra 18-99397 CDM trigger fit? The Sierra 18-99397 fits Mercury/Mariner 6 cylinder outboards including the 135, 140, 150, 175, 200, and 240 HP SportJet models from 2000 to 2007.

Which OEM part numbers does this trigger replace? It replaces Mercury/Mariner OEM part numbers 96455A18 and 96455T18, so it can be used as a direct swap for either of those numbers.

What does a CDM trigger actually do? A CDM trigger signals the Capacitor Discharge Module at the precise moment to fire the spark for each cylinder, so the 18-99397 keeps ignition timing synchronized across all six cylinders of the outboard.

How much does the 18-99397 trigger weigh? The Sierra 18-99397 CDM trigger weighs 0.4 pounds.

What are the dimensions of this part? The 18-99397 measures 6 x 6 x 1.75 inches.

What symptoms indicate this trigger needs replacement? Misfiring, rough idle, hard starting, or a no-spark condition on one or more cylinders are common signs that the CDM trigger on a Mercury/Mariner 6 cylinder outboard has failed and needs replacement with a part like the 18-99397.

Is the 18-99397 an exact match for the 96455A18 and 96455T18 triggers? Yes, the Sierra 18-99397 is built to the same fitment as the 96455A18 and 96455T18 OEM triggers, covering the same 2000-2007 Mercury/Mariner 6 cylinder engines.

Does this trigger fit 4 cylinder Mercury outboards? No, the 18-99397 is designed specifically for 6 cylinder Mercury/Mariner outboards, not 4 cylinder engines.

Can this trigger be used on the 240 HP SportJet? Yes, the 240 HP SportJet is one of the 6 cylinder engines covered by the Sierra 18-99397, alongside the 135, 140, 150, 175, and 200 HP models.

What years of Mercury/Mariner 6 cylinder outboards use this trigger? Model years 2000 through 2007 use the 18-99397 CDM trigger on the 135-240 HP 6 cylinder SportJet engine range.