# 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

  

🔄 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

  

🚤 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

  

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

  

📦 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

## Details

- **Price:** 52.5 AUD
- **Vendor:** Sawley's Auto and Marine
- **Tags:** Sawley’s AAM Used Parts – Timing Components | Timing Chains Gears & Components

## Variants

| Variant | Price | Available |
|---------|-------|-----------|
| Default Title | 52.50 AUD | In stock |

## Images

- 855746A1 Mercury Trigger Assy | Genuine Used Part
- 855746A1 Mercury Trigger Assy | Genuine Used Part
- 855746A1 Mercury Trigger Assy | Genuine Used Part
- 855746A1 Mercury Trigger Assy | Genuine Used Part
- 855746A1 Mercury Trigger Assy | Genuine Used Part
- 855746A1 Mercury Trigger Assy | Genuine Used Part

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> Source: [Sawley's Auto and Marine](https://www.sawleysautoandmarine.com.au/products/855746a1-mercury-trigger-assy-genuine-used-part)
> Updated: 2026-07-12