Spark Plug Wire Set – Fits MerCruiser 5.0L-6.2L MPI (Replaces 84-863656A1)
Spark Plug Wire Set – Fits MerCruiser 5.0L-6.2L MPI (Replaces 84-863656A1) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Spark Plug Wire Set – Fits MerCruiser 5.0L-6.2L MPI (Replaces 84-86...
Product Details
This high-performance Mercruiser Spark Plug Wire Set is engineered for V-8 MerCruiser stern drive and inboard engines (5.0L, 5.7L, and 6.2L MPI) equipped with the ECM 555 electronic control module. It is a direct fit for models with serial numbers from 0M300000 through 2A455878.
This set serves as a direct cross-reference for Mercury/Quicksilver 84-863656A1, Sierra 18-8828-1, and Indmar 756003/S756003.
- Designed as a direct OEM replacement for straightforward installation.
- Features a flat cap style connection for the Delco HVS / ECM 555 ignition system.
- Constructed with a durable Silicone/Kevlar core for superior insulation and longevity.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket brands.
| Brand | Part Number |
|---|---|
| Mercury/Quicksilver | 84-863656A1 |
| Mercury/Quicksilver | 863656A1 |
| Sierra | 18-8828-1 |
| Indmar | 756003 |
| Indmar | S756003 |
Engine & Model Compatibility
Confirm your engine model and year in the table below.
For MerCruiser engines, please verify your serial number against the notes column to ensure correct fitment, as year ranges can overlap.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| MerCruiser | 350 MAG MPI Alpha/Bravo | 300 | 4-Stroke | 2001–Up | 84-863656A1 | For engines with s/n 0M300000-Up |
| MerCruiser | 350 MAG MPI Alpha/Bravo EC | 300 | 4-Stroke | 2001–Up | 84-863656A1 | For engines with s/n 1A300000-Up |
| MerCruiser | 350 MAG MPI Horizon Alpha/Bravo | 300 | 4-Stroke | 2001–2013 | 84-863656A1 | For engines with s/n 0M300000-1A299999 |
| MerCruiser | 350 MAG MPI Horizon Alpha/Bravo EC | 300 | 4-Stroke | 2001–Up | 84-863656A1 | For engines with s/n 1A300000-Up |
| MerCruiser | 350 MAG MPI Horizon MIE | 300 | 4-Stroke | 2001–2013 | 84-863656A1 | For engines with s/n 0M310000-1A089999 |
| MerCruiser | 350 MAG MPI MIE | 300 | 4-Stroke | 2001–2013 | 84-863656A1 | For engines with s/n 0M310000-1A089999 |
| MerCruiser | 350 MAG MPI SKI | 300 | 4-Stroke | 2001–2013 | 84-863656A1 | For engines with s/n 0M300000-1A089999 |
| MerCruiser | 357 HRZ Bobtail RM | 315 | 4-Stroke | 2001–Up | 84-863656A1 | ECM 555 ignition |
| MerCruiser | 377 MAG MPI Bravo | 320 | 4-Stroke | 2001–Up | 84-863656A1 | For engines with s/n 1A300000-Up |
| MerCruiser | 377 MAG MPI Bravo EC | 320 | 4-Stroke | 2001–Up | 84-863656A1 | For engines with s/n 1A343300-Up |
| MerCruiser | 383 MAG Stroker Bravo | 350 | 4-Stroke | 2001–Up | 84-863656A1 | ECM 555 ignition |
| MerCruiser | 383 MAG Stroker Inboard | 350 | 4-Stroke | 2001–Up | 84-863656A1 | ECM 555 ignition |
| MerCruiser | 385 Performance Tuned | 385 | 4-Stroke | 2001–Up | 84-863656A1 | ECM 555 ignition |
| MerCruiser | 5.0L MPI Alpha/Bravo | 260 | 4-Stroke | 2001–Up | 84-863656A1 | For engines with s/n 0M300000-Up |
| MerCruiser | 5.0L MPI Alpha/Bravo EC | 260 | 4-Stroke | 2001–Up | 84-863656A1 | For engines with s/n 1A300000-Up |
| MerCruiser | 5.7L MPI Horizon MIE | 350 | 4-Stroke | 2013–Up | 84-863656A1 | For engines with s/n 1A090000-Up |
| MerCruiser | 5.7L MPI MIE | 350 | 4-Stroke | 2013–Up | 84-863656A1 | For engines with s/n 1A090000-Up |
| MerCruiser | 5.7L MPI MIE EC | 350 | 4-Stroke | 2013–Up | 84-863656A1 | For engines with s/n 1A090000-Up |
| MerCruiser | 5.7L MPI SKI | 350 | 4-Stroke | 2013–Up | 84-863656A1 | For engines with s/n 1A090000-Up |
| MerCruiser | 5.7L MPI TOW | 350 | 4-Stroke | 2013–Up | 84-863656A1 | ECM 555 ignition |
| MerCruiser | 5.7L MPI Towsport with GEN III | 350 | 4-Stroke | 2013–Up | 84-863656A1 | For engines with s/n 1A091881-Up |
| MerCruiser | 5.7L SKI EC | 350 | 4-Stroke | 2013–Up | 84-863656A1 | For engines with s/n 1A090000-Up |
| MerCruiser | 6.2L MPI Horizon MIE | 320 | 4-Stroke | 2013–Up | 84-863656A1 | For engines with s/n 1A090000-Up |
| MerCruiser | 6.2L MPI MIE | 320 | 4-Stroke | 2013–Up | 84-863656A1 | For engines with s/n 1A090000-Up |
| MerCruiser | 6.2L MPI MIE EC | 320 | 4-Stroke | 2013–Up | 84-863656A1 | For engines with s/n 1A091600-Up |
| MerCruiser | MX 6.2L MPI Bravo | 320 | 4-Stroke | 2001–2013 | 84-863656A1 | For engines with s/n 0M300000-1A299999 |
| MerCruiser | MX 6.2L MPI Horizon Bravo | 320 | 4-Stroke | 2001–2013 | 84-863656A1 | For engines with s/n 0M300000-1A299999 |
| MerCruiser | MX 6.2L MPI Horizon MIE | 320 | 4-Stroke | 2001–2013 | 84-863656A1 | For engines with s/n 0M310000-1A089999 |
| MerCruiser | MX 6.2L MPI MIE | 320 | 4-Stroke | 2001–2013 | 84-863656A1 | For engines with s/n 0M310000-1A089999 |
| MerCruiser | MX 6.2L MPI SKI | 320 | 4-Stroke | 2001–2007 | 84-863656A1 | For engines with s/n 0M317000-0W689999 |
Technical Specs
- Product Type
- Spark Plug Wire Set
- Installation
- Direct OEM replacement
- Fuel Type
- Gasoline
- Housing Material
- Silicone/Kevlar core with insulation
- Connection
- Flat cap style for ECM 555 ignition
- Ignition System
- For use with Delco HVS ignition system
- Warranty
- 1 year factory warranty
What’s in the Box
- 1 x Spark Plug Wire Set (84-863656A1)
Installation Notes
- Disconnect the boat's battery before starting work.
- To avoid mixing up the firing order, replace only one spark plug wire at a time. Remove the old wire and immediately replace it with the new one of the same length.
- Ensure each wire boot snaps securely onto both the spark plug and the distributor cap. A loose connection can cause a misfire.
- Carefully route the new wires, keeping them clear of hot exhaust manifolds and any sharp edges to prevent damage.
- Once all wires are replaced, reconnect the battery and start the engine to confirm it runs smoothly.
Troubleshooting & FAQ
How do I know if this wire set fits my engine?
This set is specifically for V-8 MerCruiser MPI engines (5.0L, 5.7L, 6.2L) that use the ECM 555 system and have serial numbers between 0M300000 and 2A455878. Always check the detailed compatibility table and confirm your engine's serial number before ordering.
What are the signs of old or failing spark plug wires?
Common symptoms include rough idling, engine misfires (especially under load), hesitant acceleration, decreased fuel economy, and visible damage like cracks, burns, or corrosion on the wire boots.
How often should I replace my spark plug wires?
There is no fixed replacement interval, but it is good practice to inspect them during every tune-up. We recommend replacing them every 5-7 years or whenever you notice signs of electrical leakage, physical wear, or a decline in engine performance.
Can I use these wires with a different type of ignition?
No. This wire set is engineered specifically for the Delco HVS ignition system which uses a flat-style distributor cap (ECM 555). Using it with a different system may lead to poor fitment and incorrect ignition performance.
What is the difference between this set and the OEM original?
This is a high-quality aftermarket part designed to meet or exceed original equipment manufacturer (OEM) specifications for electrical performance, fit, and durability. It provides comparable function at a better value.
Is any special tool required for installation?
No special tools are required for installation. However, using a spark plug wire puller can make it easier to remove the old wires without damaging the boots or distributor cap terminals.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost?
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns?
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
Payment & Security
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