Sierra MagForce 4-Cylinder MerCruiser 470 Spark Plug Wire Set - 18-8808-2
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The Sierra 18-8808-2 is a MagForce premium marine 4-cylinder spark plug wire set for select vintage MerCruiser inline-4 sterndrive engines using compatible conventional distributor ignition systems. This 5-lead kit is commonly associated with classic MerCruiser 3.7L / 470-series engines where the ignition layout, distributor style, coil location, and wire lengths match the Sierra application chart.
Built for marine engine compartments, this wire set helps deliver consistent ignition output while providing suppression against ignition-related radio frequency interference around onboard electronics.
Key Features
- Sierra MagForce premium marine spark plug wire set.
- Sierra part number: 18-8808-2.
- Designed for select 4-cylinder MerCruiser sterndrive applications.
- Includes 5 total leads: 4 spark plug wires plus 1 coil wire.
- 8 mm heavy-duty ignition wire profile.
- Spiral-wound stainless-style conductor design for ignition suppression and spark delivery.
- Silicone-style jacketing and boots for marine heat and moisture exposure.
- Corrosion-resistant terminal construction for marine ignition service.
- Intended for compatible conventional distributor ignition layouts where specified by application chart.
Kit Contents & Wire Lengths
This set includes the following wire lengths:
- 1 coil wire — 13 in.
- 1 spark plug wire — 23 in.
- 1 spark plug wire — 26 in.
- 1 spark plug wire — 34 in.
- 1 spark plug wire — 39 in.
Confirm each lead length and terminal end against the original wire set before installation.
Engine Compatibility
Common application context includes select vintage MerCruiser 4-cylinder sterndrive engines by model, serial range, ignition system, and application chart, including:
- MerCruiser 470 applications where specified
- MerCruiser 485 applications where specified
- MerCruiser 488 applications where specified
- MerCruiser 3.7L applications where specified
- MerCruiser 3.7LX applications where specified
- Select 165 HP to 190 HP 3.7L inline-4 MerCruiser platforms where the distributor style and wire routing match this kit
Use this wire set only where the Sierra application chart or engine service information confirms 18-8808-2 as the correct replacement.
Fitment Notice
Confirm fitment by engine serial number, ignition system, distributor cap style, coil location, plug boot angle, terminal style, and original wire routing before ordering. MerCruiser 3.7L / 470-series engines can have different ignition components depending on production range and service history, so engine family alone is not enough to confirm the correct wire set.
When This Part Needs Replacement
Replace spark plug wires if the engine has hard starting, rough idle, misfire under load, weak acceleration, visible arcing, burned insulation, cracked boots, corroded terminals, loose plug connections, or high resistance in one or more leads. Wires should also be inspected during distributor cap, rotor, spark plug, points, condenser, and seasonal ignition service.
Installation Notes
Replace one wire at a time to preserve the correct firing order. Match each new lead to the closest original length and route it through the factory wire separators or retainers. Keep wires away from exhaust manifolds, belts, pulleys, sharp brackets, and hot engine surfaces. Push each boot fully onto the spark plug, distributor cap, and coil terminal until it seats securely.
For conventional ignition systems, inspect the distributor cap, rotor, points, condenser, and point gap while replacing the wires. Worn or pitted ignition points can still cause weak spark even with a new wire set installed.
Alternate/Cross-Reference Part Numbers
- Sierra 18-8808-2 — MagForce premium marine spark plug wire set
- Mercury 84-816761Q6 — cross-reference; verify by engine and ignition layout
- Mercury 84-813720A6 — cross-reference; verify by engine and ignition layout
- Mercury 84-43376A6 — cross-reference; verify by engine and ignition layout
- Mallory 9-28014 — cross-reference; verify by application
Parts Desk Insight
The 18-8808-2 is a layout-specific wire set for classic 4-cylinder MerCruiser ignition systems. Before replacing wires, confirm the distributor type and compare the existing lead lengths. On older 470-series engines, ignition complaints often come from a combination of aged wires, worn cap and rotor contacts, incorrect point gap, and heat-damaged routing near the exhaust side of the engine.
Shipping: Ships same or next day for fast Canada wide shipping. ⚓
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
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If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
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Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
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