7-Inch Spark Plug Wire for Mercury/Mariner Outboard Ignition Systems – Sierra 18-8819-1 Replacement
7-Inch Spark Plug Wire for Mercury/Mariner Outboard Ignition Systems – Sierra 18-8819-1 Replacement is backordered and will ship as soon as it is back in stock.
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7-Inch Spark Plug Wire for Mercury/Mariner Outboard Ignition System...
7-Inch Spark Plug Wire for Mercury/Mariner Outboard Ignition Systems – Sierra 18-8819-1 Replacement is backordered and will ship as soon as it is back in stock.
Product Details
This 7-inch spark plug wire is an aftermarket replacement lead for selected Mercury and Mariner outboard ignition applications. It is intended for replacing a worn or damaged wire when the original wire matches the same length, terminal style, boot configuration, and cylinder position.
The wire is listed as a replacement for Sierra 18-8819-1. It is supplied as one individual wire, not as a complete engine wire set. Always compare the original wire and verify the application before ordering.
- 7-inch individual spark plug wire for selected marine ignition applications.
- Designed as a direct replacement when the original part has the same specifications.
- Suitable for routine ignition-system maintenance or replacement of a damaged lead.
- Check the required wire length and cylinder position before installation; other positions may use different lengths.
Part Number Reference
The following reference identifies the listed replacement application for this 7-inch wire.
| Brand | Reference | Description |
|---|---|---|
| Sierra | 18-8819-1 | 7-inch spark plug wire, 8 mm |
Important: Mercury reference 84-813715A1 is associated with different 9-inch wire listings and should not be used to identify this 7-inch wire.
Engine and Application Compatibility
This wire is intended for selected Mercury/Mariner outboard ignition systems, but the available reference information does not establish universal fitment across every 150–200 HP model, year, serial range, or cylinder position. Confirm the complete engine model, stroke, serial range, original wire length, and terminal configuration before purchase.
| Application | Fitment Guidance |
|---|---|
| Mercury/Mariner outboard ignition systems | Use only where the original wire is a matching 7-inch, 8 mm lead with the same ends and routing. |
| Other cylinder positions | May require a different wire length. Do not substitute this wire solely because the engine horsepower is similar. |
Technical Specifications
- Product Type
- Individual spark plug wire
- Length
- 7 inches (approximately 178 mm)
- Wire Size
- 8 mm
- Application
- Selected Mercury/Mariner outboard ignition systems
- Installation
- Replacement installation using the original routing and connection points
- Package Quantity
- 1 spark plug wire
- Reference Part
- Sierra 18-8819-1
- Product Status
- Aftermarket replacement; not an OEM Mercury component
What's in the Box
- 1 x 7-inch spark plug wire
Installation Notes
- Disconnect power: Turn off the engine and disconnect the battery according to the manufacturer's safety procedure.
- Replace one wire at a time: Keep the original routing and firing-order connections correctly identified.
- Remove the old wire: Grip the boot rather than pulling on the wire itself. Twist gently if needed before removing it from the spark plug and ignition end.
- Compare before fitting: Confirm the new wire is the same length and has matching boots and terminals.
- Install the replacement: Push each boot firmly onto its connection point. Use dielectric grease only if recommended for the application.
- Inspect the installation: Make sure the wire is routed away from hot surfaces and moving components before testing the engine.
Troubleshooting & FAQ
Is this a complete spark plug wire set?
No. This listing is for one individual 7-inch spark plug wire. Other cylinder positions may require wires of different lengths.
How do I confirm that the 7-inch length is correct?
Measure the existing wire and compare its boots, terminals, routing, and cylinder position. Do not choose this wire based on horsepower alone.
Does this wire replace Mercury 84-813715A1?
No fitment equivalence is stated here. Catalog information associates 84-813715A1 with separate 9-inch wire listings, while this product is a 7-inch wire associated with Sierra 18-8819-1.
What are common signs of a worn spark plug wire?
Possible symptoms include intermittent misfire, rough running, poor acceleration, or visible cracking, burn marks, corrosion, or damaged boots. Diagnose the ignition system before replacing parts.
Is this an OEM Mercury part?
No. This is an aftermarket replacement wire and is not manufactured or branded as an OEM Mercury component.
Safety and Important Information
- Verify the original wire's length, terminals, boots, engine model, stroke, serial range, and cylinder position before ordering.
- Do not assume that every Mercury or Mariner 150–200 HP engine uses the same wire length.
- Do not use 84-813715A1 as the identification reference for this 7-inch wire.
- Professional installation is recommended when the ignition system or firing order is uncertain.
About Sea Sierra
- Marine Replacement Parts — Practical aftermarket components for maintenance and repair applications.
- Application-Focused Listings — Product references and fitment guidance are provided to help match the original part.
- Support for Correct Selection — Compare the original component and engine identification details before ordering.
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