# 339-7452A3 Mercury Switch Box | Genuine Used Part

🔧 Product Description

  

Genuine Mercury Switch Box / CDI Module - Part Number: 339-7452A3

  

A genuine Mercury switch box / CDI ignition module used on selected Mercury and Mariner two-cylinder two-stroke outboards. This capacitor discharge ignition pack controls spark triggering from the stator and trigger circuits to the ignition coils.

  

⚙️ Key Features

  

• Genuine Mercury switch box / CDI module

• Correct Mercury part number 339-7452A3

• Used on selected 18HP, 20HP, 25HP, 35HP and 40HP two-cylinder Mercury / Mariner engines

• Cross-references with CDI Electronics 114-7452A3

• Also crosses with Sierra 18-5776 and Mallory 9-25101 style replacements

  

🔄 Supersession & Cross Reference

  

OEM Supersession Chain:

  

• 339-7452A3 Mercury switch box reference

• 339-7452A2 earlier related Mercury switch box reference

• 339-7452A1 earlier related Mercury switch box reference

  

OEM / Related Numbers:

  

• 339-7452A3

• 3397452A3

• 7452A3

• 339-7452A2

• 3397452A2

• 7452A2

• 339-7452A1

• 3397452A1

• 7452A1

• 899883230

• Switch box

• CDI module

• Capacitor discharge ignition pack

• Ignition switch box

  

Aftermarket / Verified Equivalents:

  

• CDI Electronics: 114-7452A3

• Sierra: 18-5776

• Mallory: 9-25101

  

🚤 Compatibility

  

Commonly used on:

  

• Mercury / Mariner two-cylinder two-stroke CDI ignition systems

  

Typically suits:

  

• Engine models:

• Mercury 18HP 2-cylinder two-stroke - 1980-1987

• Mercury 20HP 2-cylinder two-stroke - 1980-1987

• Mercury 25HP 2-cylinder two-stroke - 1980-1987

• Mercury 35HP 2-cylinder two-stroke - 1980-1987

• Mercury 40HP 2-cylinder two-stroke - 1980-1987

• Mariner 18HP 2-cylinder two-stroke - 1980-1987

• Mariner 20HP 2-cylinder two-stroke - 1980-1987

• Mariner 25HP 2-cylinder two-stroke - 1980-1987

• Mariner 35HP 2-cylinder two-stroke - 1980-1987

• Mariner 40HP 2-cylinder two-stroke - 1980-1987

  

• HP Range: 18HP - 40HP

• Engine Type: Mercury / Mariner two-cylinder two-stroke outboard CDI ignition system

• Year Range: approximately 1980 - 1987

• Serial Note: Match by exact Mercury / Mariner serial number, original switch-box number, wiring colours, connector style and ignition-system diagram before installation.

  

🔌 Function

  

The switch box receives stator and trigger inputs, stores ignition energy and fires the ignition coils at the correct timing point.

  

Common signs of failure:

  

• No spark on one or both cylinders

• Weak or intermittent spark

• Engine starts then loses spark

• Misfire under load

• Heat-related ignition failure

• Kill circuit or stop wire fault damaging the module

• Spark returns when a known-good switch box is fitted

• Burnt, cracked or corroded switch-box terminals

  

📦 Condition

  

• Genuine used part

• Removed from running engine where applicable

• In good working condition unless otherwise stated

## Details

- **Price:** 45.0 AUD
- **Vendor:** Sawley's Auto and Marine
- **Tags:** Sawley’s AAM Used Parts – Electronic Components | ECU CDI & Electrical Parts

## Variants

| Variant | Price | Available |
|---------|-------|-----------|
| Default Title | 45.00 AUD | In stock |

## Images

- 339-7452A3 Mercury Switch Box | Genuine Used Part

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> Source: [Sawley's Auto and Marine](https://www.sawleysautoandmarine.com.au/products/339-7452a3-mercury-switch-box-genuine-used-part)
> Updated: 2026-07-02