---
product_id: 97819868
title: "Replacement Inboard Ignition Coil - Compatible with MerCruiser Thunderbolt IV and V Ignition Systems with HEI - Replaces 18-5438, 392-805570A2, 392-7803A4, 392-805570A1, 72115, 40511"
brand: "aa ignition"
price: "£32.77"
currency: GBP
in_stock: true
reviews_count: 13
category: "Aa Ignition"
url: https://www.desertcart.co.uk/products/97819868-replacement-inboard-ignition-coil-compatible-with-mercruiser-thunderbolt-iv-v
store_origin: GB
region: United Kingdom
---

# High Energy Ignition (HEI) compatible Plug & play OEM direct replacement Fits MerCruiser Thunderbolt IV & V engines Replacement Inboard Ignition Coil - Compatible with MerCruiser Thunderbolt IV and V Ignition Systems with HEI - Replaces 18-5438, 392-805570A2, 392-7803A4, 392-805570A1, 72115, 40511

**Brand:** aa ignition
**Price:** £32.77
**Availability:** ✅ In Stock

## Summary

> ⚡ Ignite your boat’s performance — don’t let a faulty coil slow your adventure!

## Quick Answers

- **What is this?** Replacement Inboard Ignition Coil - Compatible with MerCruiser Thunderbolt IV and V Ignition Systems with HEI - Replaces 18-5438, 392-805570A2, 392-7803A4, 392-805570A1, 72115, 40511 by aa ignition
- **How much does it cost?** £32.77 with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.co.uk](https://www.desertcart.co.uk/products/97819868-replacement-inboard-ignition-coil-compatible-with-mercruiser-thunderbolt-iv-v)

## Best For

- aa ignition enthusiasts

## Why This Product

- Trusted aa ignition brand quality
- Free international shipping included
- Worldwide delivery with tracking
- 15-day hassle-free returns

## Key Features

- • **DIY Friendly:** Simple plug-in installation saves time and dealer costs.
- • **Built to Last:** Backed by a 2-year/24,000-mile warranty for worry-free boating.
- • **Revive Your Ride:** Restore smooth starts and peak engine power instantly.
- • **Precision Compatibility:** Tailored for MerCruiser GM V6/V8 308-8.2L engines with Thunderbolt IV & V HEI systems.
- • **OEM Quality Without the Price:** Engineered by original equipment suppliers for perfect fit and finish.

## Overview

This AA Ignition replacement coil is a direct-fit, high-energy ignition component designed specifically for MerCruiser Thunderbolt IV and V HEI marine engines ranging from 4.3L to 8.2L. It ensures reliable spark delivery for smooth starts and consistent power, comes with a 2-year or 24,000-mile warranty, and offers a cost-effective alternative to OEM parts with easy plug-in installation.

## Description

Product description Inboard Ignition Coil Other Parts for your Vehicle Water Circulating Pump Electric Fuel Pump Distributor Cap Tune Up

Review: No issues so far … - So far so good !!
Review: Great value, good quality and low price - It was great to see that this coil for my Mercruiser 5.7L actually had brass terminal posts. After the problems about inferior terminals on other manufactures coils, namely aluminum or some sort of pot metal, that were easily broken as they were tightened, this coil had stronger brass posts and even came with the nuts tightened and the lock washers compressed. That told me this coil had a good chance of being installed without breaking anything. With a two year warranty, what's to lose?

## Features

- Replacement Inboard Marine Engine Ignition Coil - The ignition coils or ignition coil plug provides spark for your engine. Over time the factory ignition coil packs can fail, leading to hard starting, losing power when the engine is hot, or your boat may run erratically. Replace your faulty ignition coil and restore performance and driveability on your boat.
- Compatible with Mercruiser GM V6, V8 308 & 350 Engine With Thunderbolt IV & V Ignition System - Only works with HEI (High Energy Ignition) Systems and will not work with Point Ignition Systems. This replacement ignition coil by AA Ignition, made by an original equipment supplier, will get your 4.3L, 5.0L, 5.7L, 6.2L, 7.4L & 8.2L petrol engines with Thunderbolt 4 and 5 ignition systems back up and running properly.
- Replaces Part# 18-5438, 392-805570A2, 392-7803A4, 392-805570A1, 72115, 40511, 9-29701, 64570, RL5438. The ignition coil of your boat can easily be located beside the distributor, which is found in the engine.
- OEM Fit, Quality & Finish - While this is not a genuine OEM part, it is a direct replacement for your boat or boat engine and it will appear, fit and work like the factory part. Save time and hundreds of dollars off of dealer prices by replacing the part yourself.
- 2 years or 24,000 Mile Warranty - This mercruiser ignition coil pack comes complete with a 2 year or 24, 000 mile warranty. If the coil ever fails on your boat within the warranty period, simply contact us for a free replacement. See our website for full details.

## Technical Specifications

| Specification | Value |
|---------------|-------|
| ASIN | B07GL4TM27 |
| Automotive Fit Type | Vehicle Specific Fit |
| Best Sellers Rank | #25,318 in Automotive ( See Top 100 in Automotive ) #46 in Automotive Replacement Ignition Coils |
| Brand | AA Ignition |
| Brand Name | AA Ignition |
| Compatible with Vehicle Type | Boat |
| Connector Gender | Male-to-Female |
| Customer Reviews | 4.5 out of 5 stars 862 Reviews |
| EU Spare Part Availability Duration | 2 Years |
| Installation Type | Plug In |
| Item Weight | 0.6 Kilograms |
| Manufacturer | AA Ignition |
| Manufacturer Part Number | 18-5438 |
| Manufacturer Warranty Description | 2 Years or 24,000 Miles |
| Model Number | 18-5438 |
| OEM Equivalent Part Number | 18-5438, 3000-8M0079202, 392-7803, 64570, RL5438, 392-805570A2, 392-7803A4, 392-805570A1, 72115, 40511, 9-29701 |
| Part Interchange Info | replacement |
| Vehicle Service Type | Boat |

## Product Details

- **Brand:** AA Ignition
- **Vehicle Service Type:** Boat
- **Item Weight:** 0.6 Kilograms
- **Connector Gender:** Male-to-Female
- **Installation Type:** Plug In

## Images

![Replacement Inboard Ignition Coil - Compatible with MerCruiser Thunderbolt IV and V Ignition Systems with HEI - Replaces 18-5438, 392-805570A2, 392-7803A4, 392-805570A1, 72115, 40511 - Image 1](https://m.media-amazon.com/images/I/61R3DWNZO7L.jpg)
![Replacement Inboard Ignition Coil - Compatible with MerCruiser Thunderbolt IV and V Ignition Systems with HEI - Replaces 18-5438, 392-805570A2, 392-7803A4, 392-805570A1, 72115, 40511 - Image 2](https://m.media-amazon.com/images/I/71cz82gZCBL.jpg)
![Replacement Inboard Ignition Coil - Compatible with MerCruiser Thunderbolt IV and V Ignition Systems with HEI - Replaces 18-5438, 392-805570A2, 392-7803A4, 392-805570A1, 72115, 40511 - Image 3](https://m.media-amazon.com/images/I/71Nds3+8drL.jpg)
![Replacement Inboard Ignition Coil - Compatible with MerCruiser Thunderbolt IV and V Ignition Systems with HEI - Replaces 18-5438, 392-805570A2, 392-7803A4, 392-805570A1, 72115, 40511 - Image 4](https://m.media-amazon.com/images/I/91i8ZTfENGL.jpg)
![Replacement Inboard Ignition Coil - Compatible with MerCruiser Thunderbolt IV and V Ignition Systems with HEI - Replaces 18-5438, 392-805570A2, 392-7803A4, 392-805570A1, 72115, 40511 - Image 5](https://m.media-amazon.com/images/I/81lFG8BRRQL.jpg)

## Customer Reviews

### ⭐⭐⭐⭐⭐ No issues so far …
*by A***R on September 15, 2025*

So far so good !!

### ⭐⭐⭐⭐⭐ Great value, good quality and low price
*by T***D on July 21, 2021*

It was great to see that this coil for my Mercruiser 5.7L actually had brass terminal posts. After the problems about inferior terminals on other manufactures coils, namely aluminum or some sort of pot metal, that were easily broken as they were tightened, this coil had stronger brass posts and even came with the nuts tightened and the lock washers compressed. That told me this coil had a good chance of being installed without breaking anything. With a two year warranty, what's to lose?

### ⭐⭐⭐⭐ As described
*by K***R on September 6, 2025*

works great

## Frequently Bought Together

- Replacement Inboard Ignition Coil - Compatible with MerCruiser Thunderbolt IV and V Ignition Systems with HEI - Replaces 18-5438, 392-805570A2, 392-7803A4, 392-805570A1, 72115, 40511
- THUNDERBOLT Distributor Cap and trigger wheel Rotor Kit with gasket and screws for Mercruiser 5.0, 5.7, 7.4, 8.2 5.0L 5.7L 7.4L 8.2L V8 engines 805759Q3, 805759T3 18-5935.
- B. Ignition Sensor Kit for MerCruiser Thunderbolt I IV Distributor

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**Shop now:** [https://www.desertcart.co.uk/products/97819868-replacement-inboard-ignition-coil-compatible-with-mercruiser-thunderbolt-iv-v](https://www.desertcart.co.uk/products/97819868-replacement-inboard-ignition-coil-compatible-with-mercruiser-thunderbolt-iv-v)

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*Product available on Desertcart United Kingdom*
*Store origin: GB*
*Last updated: 2026-05-16*