855746A1 Mercury Trigger Assy | Genuine Used Part

🔧 Product Description

Genuine Used Mercury Mariner Three-Cylinder CDM Short-Arm Trigger - Part Number: 855746A1

A genuine pre-owned Mercury and Mariner trigger assembly for selected three-cylinder CDM-ignition outboards and jet-drive engines.

The trigger is mounted beneath the flywheel and provides crankshaft-position signals to the engine's CDM ignition modules. This version uses the short spark-advance arm configuration.

⚙️ Key Features

• Genuine Mercury or Mariner used trigger
• Correct OEM reference 855746A1
• Three-cylinder CDM ignition configuration
• Short-arm trigger design
• Suitable for selected 30HP through 90HP families
• CDI, Sierra and aftermarket replacements available

🚤 Compatibility

Commonly used on selected

• Mercury 30HP three-cylinder engines
• Mercury 40HP three-cylinder engines
• Mercury 50HP
• Mercury 55HP
• Mercury 60HP
• Mercury 75HP
• Mercury 90HP
• 30 Jet, 40 Jet, 45 Jet and 65 Jet applications
• Compatible Mariner three-cylinder engines

Important fitment note

• Confirm the engine has three cylinders and CDM ignition.
• Do not confuse this short-arm three-cylinder trigger with the four-cylinder 855746A2 assembly.
• Compare wire colours, arm length and connector layout.

🔌 Function

The trigger produces position signals used by the CDM ignition modules to determine when each spark plug should fire.

⚠️ Common Signs of Failure

• No spark on one or more cylinders
• Intermittent spark
• Engine stalls when warm
• Misfire at a repeatable rpm
• Difficult starting
• Engine will not accelerate correctly
• Trigger wiring is damaged
• Timing signal is absent or unstable

🛠️ Service Notes

Recommended checks before installation

• Confirm the cylinder count and arm length
• Test trigger resistance and peak voltage
• Inspect CDM modules, stator and wiring
• Check the flywheel magnets
• Confirm free movement through the advance range
• Set timing and synchronisation after installation

🔄 Supersession & Cross Reference

OEM Supersession / Related Chain

• 834520T - Related OEM trigger reference
• 854512T - Later service trigger
• 855746A1 - OEM assembly reference
• 855746A12 - Related service-kit reference

OEM / Related Numbers

• 855746A1
• 855746A12
• 854512T
• 834520T
• Trigger Type: Three-Cylinder CDM Short Arm

Aftermarket / Verified Equivalents

• CDI Electronics: 134-4512-3
• Sierra: 18-99396
• Aftermarket replacement for 854512T
• Aftermarket replacement for 855746A1 / 855746A12

📦 Condition

• Genuine Mercury or Mariner used part
• Pre-owned electrical component
• Cosmetic marks, wire ageing and oxidation may be present
• Electrical testing before installation is strongly recommended
• Supplied in protective or equivalent packaging