9-Inch 7mm Spark Plug Wire for Select Mercury/Mariner Outboards – Replaces Mercury 84-813715A1
9-Inch 7mm Spark Plug Wire for Select Mercury/Mariner Outboards – Replaces Mercury 84-813715A1 is backordered and will ship as soon as it is back in stock.
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9-Inch 7mm Spark Plug Wire for Select Mercury/Mariner Outboards – R...
9-Inch 7mm Spark Plug Wire for Select Mercury/Mariner Outboards – Replaces Mercury 84-813715A1 is backordered and will ship as soon as it is back in stock.
Product Details
This 9-inch 7mm spark plug wire is an aftermarket replacement lead for select Mercury and Mariner outboard ignition systems. It is designed to transfer ignition energy from the ignition system to the spark plug and is listed as a replacement for Mercury OEM part 84-813715A1.
The wire is also cross-referenced with Sierra part 18-5227-1. Because Mercury and Mariner outboards use different wire lengths, engine configurations, and serial-number ranges, confirm the OEM number, wire length, terminal arrangement, and existing wire size before ordering.
- Single 9-inch spark plug wire.
- 7mm wire construction with a silicone outer jacket.
- Metallic/magnetic suppression-style core for ignition noise control.
- Designed as a direct replacement when the listed part number and dimensions match.
- Aftermarket replacement; not manufactured by Mercury Marine or Sierra.
Part Number Matrix
Use the following references to compare the replacement wire with your original part. Part-number references do not replace verification of the complete engine application.
| Brand or source | Part number | Reference type |
|---|---|---|
| Mercury | 84-813715A1 | OEM reference |
| Sierra | 18-5227-1 | Aftermarket cross-reference |
Engine and Model Compatibility
This wire is intended for selected Mercury and Mariner outboard applications that use Mercury OEM reference 84-813715A1. Application listings associate this reference with multiple engine families and serial-number conditions, so the OEM number alone should not be treated as universal fitment.
Before purchasing, compare the replacement with the wire being removed and verify all of the following:
- Mercury or Mariner brand and exact engine model.
- Engine horsepower, stroke type, and serial-number range.
- Required 9-inch length and 7mm wire size.
- Terminal and boot style at both ends.
- OEM reference 84-813715A1 or aftermarket reference 18-5227-1.
Do not use this listing as confirmation for an engine application that uses a different OEM number, a different wire length, or a different wire size.
Technical Specifications
- Product type
- Single spark plug wire
- Length
- 9 inches (approximately 229 mm)
- Wire size
- 7mm
- Core
- Metallic/magnetic suppression-style core
- Outer jacket
- Silicone
- Application
- Select Mercury and Mariner outboard ignition systems
- OEM reference
- Mercury 84-813715A1
- Aftermarket reference
- Sierra 18-5227-1
- Color
- Black
What's in the Box
- 1 x 9-inch 7mm spark plug wire
This listing is for one wire, not a complete engine wire set. Multi-cylinder engines may require several wires of different lengths.
Installation Notes
- Disconnect power: Allow the engine to cool and disconnect the battery or ignition power before servicing the ignition system.
- Replace one wire at a time: Keep the original wire connected until the replacement is ready to install so the ignition routing is not confused.
- Remove the old wire: Hold the boot or terminal firmly and twist gently before pulling it free. Do not pull on the wire conductor.
- Inspect the connection points: Check the spark plug terminal and ignition-side terminal for corrosion, looseness, or damage.
- Install the replacement: Route the new wire along the original path and keep it away from sharp edges, hot surfaces, and moving components.
- Seat both ends: Push the spark-plug boot and ignition-side terminal fully into position. Confirm that neither connection is loose.
- Test the engine: Reconnect power and check for proper starting and smooth operation. Stop immediately if the engine misfires or the wire shows arcing.
Troubleshooting and FAQ
Is this a complete set of spark plug wires?
No. This listing includes one 9-inch spark plug wire. Engines with multiple cylinders may require several wires, and the required lengths may vary.
What part numbers does this wire replace?
This wire is listed as a replacement for Mercury OEM reference 84-813715A1 and cross-referenced with Sierra 18-5227-1. Always compare the complete application and physical dimensions before installation.
Will it fit every Mercury or Mariner 150–200 HP outboard?
No universal fitment should be assumed. Mercury and Mariner engines can use different ignition components and serial-number ranges. Confirm the exact OEM reference, model, serial number, length, wire size, and terminal style for your engine.
How do I know whether I need the 7mm or 8mm version?
This listing is for the 7mm wire. Some applications use a different 8mm wire reference, so measure or compare your existing wire and verify the applicable part number before ordering.
What are common signs of a worn spark plug wire?
Common symptoms include intermittent misfire, rough running, hard starting, poor acceleration, or visible cracking, burn marks, corrosion, or electrical arcing around the wire or boots.
Is this an OEM Mercury part?
No. This is an aftermarket replacement wire. Mercury 84-813715A1 and Sierra 18-5227-1 are provided as reference numbers for compatibility checking.
Safety and Important Information
- Verify the OEM reference, engine model, serial range, wire length, wire size, and terminal configuration before purchase.
- Do not install a wire that is damaged, incorrectly sized, or routed near hot or moving engine components.
- Disconnect the battery or ignition power before servicing ignition wiring.
- Professional installation is recommended when the correct ignition routing or terminal configuration is uncertain.
About Sea Sierra
- Marine replacement parts — We provide aftermarket components for maintenance and repair applications.
- Application-focused listings — Reference numbers and dimensional details are provided to help customers compare replacement parts.
- Support when you need it — Contact support with your exact engine model and serial number if you need help checking an application.
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