# 7452A21 Mercury CDI | Genuine Used Part

🔧 Product Description

  

Genuine Mercury Switch Box / CDI Module - Part Number: 339-7452A21

  

A genuine Mercury ignition switch box / CDI module used on selected Mercury and Mariner 2-cylinder two-stroke outboards. This bullet-connector ignition module controls spark triggering from the stator and trigger circuits to the ignition coils.

  

⚙️ Key Features

  

• Genuine Mercury CDI / switch box

• Correct Mercury part number 339-7452A21

• Bullet-connector ignition pack

• Used on selected 6HP to 35HP 2-cylinder Mercury / Mariner two-stroke outboards

• Cross-references with CDI Electronics 114-7452K1 and Sierra 18-5776 style replacements

  

🔄 Supersession & Cross Reference

  

OEM Supersession Chain:

  

• 339-7452A21 later Mercury switch box reference

• 339-7452A20 earlier related Mercury switch box reference

• 339-7452A19 earlier related Mercury switch box reference

• 339-7452A18 earlier related Mercury switch box reference

• 339-7452A15 earlier related Mercury switch box reference

• 339-7452A14 earlier related Mercury switch box reference

• 339-7452A13 earlier related Mercury switch box reference

• 339-7452A11 earlier related Mercury switch box reference

• 339-7452A10 earlier related Mercury switch box reference

• 339-7452A9 earlier related Mercury switch box reference

• 339-7452A8 earlier related Mercury switch box reference

• 339-7452A7 earlier related Mercury switch box reference

• 339-7452A1 earlier related Mercury switch box reference

  

OEM / Related Numbers:

  

• 339-7452A21

• 7452A21

• 3397452A21

• 339-7452A20

• 339-7452A19

• 339-7452A18

• 339-7452A15

• 339-7452A14

• 339-7452A13

• 339-7452A11

• 339-7452A10

• 339-7452A9

• 339-7452A8

• 339-7452A7

• 339-7452A1

• Switch box

• CDI module

• Ignition pack

  

Aftermarket / Verified Equivalents:

  

• CDI Electronics: 114-7452K1

• Sierra: 18-5776

  

🚤 Compatibility

  

Commonly used on:

  

• Mercury / Mariner 2-cylinder two-stroke bullet-connector ignition systems

  

Typically suits:

  

• Engine models:

• Mercury 6HP 2-cylinder - 1980-1997

• Mercury 8HP 2-cylinder - 1980-1997

• Mercury 9.9HP 2-cylinder - 1980-1997

• Mercury 10HP 2-cylinder - 1980-1997

• Mercury 15HP 2-cylinder - 1980-1997

• Mercury 18HP 2-cylinder - 1980-1997

• Mercury 20HP 2-cylinder - 1980-1997

• Mercury 25HP 2-cylinder - 1980-1997

• Mercury 35HP 2-cylinder - 1980-1997

• Mariner 6HP 2-cylinder - 1980-1997

• Mariner 8HP 2-cylinder - 1980-1997

• Mariner 9.9HP 2-cylinder - 1980-1997

• Mariner 10HP 2-cylinder - 1980-1997

• Mariner 15HP 2-cylinder - 1980-1997

• Mariner 18HP 2-cylinder - 1980-1997

• Mariner 20HP 2-cylinder - 1980-1997

• Mariner 25HP 2-cylinder - 1980-1997

• Mariner 35HP 2-cylinder - 1980-1997

  

• HP Range: 6HP - 35HP

• Engine Type: Mercury / Mariner 2-cylinder two-stroke outboard ignition system

• Year Range: approximately 1980 - 1997

• Serial Note: Match by engine serial number, bullet-connector pack layout and original switch-box number.

  

🔌 Function

  

The CDI / switch box stores and releases ignition energy to trigger spark at the correct timing point for the ignition coils.

  

Common signs of failure:

  

• No spark

• Weak or intermittent spark

• Engine starts then loses spark

• Misfire under load

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

• Heat-related ignition failure

• Damaged or corroded bullet connectors

  

📦 Condition

  

• Genuine used part

• Removed from running engine where applicable

• In good working condition unless otherwise stated

## Details

- **Price:** 60.0 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 | 60.00 AUD | In stock |

## Images

- 7452A21 Mercury CDI | Genuine Used Part

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> Source: [Sawley's Auto and Marine](https://www.sawleysautoandmarine.com.au/products/7452a21-mercury-cdi-genuine-used-part)
> Updated: 2026-07-02