Sierra 18-5158
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Within 30 days
Sierra 18-5158 Product Description
Upgrade Your Outboard's Spark with Sierra 18-5158 Ignition Coil
Every time you fire up your boat engine, the ignition coil plays a starring role in delivering that precise, high-voltage spark needed for smooth combustion. The Sierra 18-5158 steps in as a robust replacement for the Mercury Marine coil (MC#8M0077471), engineered to match original equipment specifications while standing up to the harsh marine environment. Crafted with premium epoxy resin encapsulation, this coil resists moisture, corrosion, and vibration—common culprits that doom lesser parts on the water.
Boat owners rave about the noticeable difference: quicker starts, steadier idling, and that extra punch at wide-open throttle. Whether you're chasing offshore species or cruising the bay, this coil ensures your engine runs at peak efficiency, minimizing downtime and maximizing those unforgettable days on the water.
Why Choose the Sierra 18-5158 for Your Marine Engine?
- Direct OEM Match: Precisely calibrated to Mercury's 8M0077471 specs, ensuring plug-and-play compatibility without modifications.
- Superior Durability: High-dielectric strength materials shield against saltwater spray, fuel vapors, and extreme temperatures from -40°F to 250°F.
- Enhanced Performance: Generates consistent 20,000-40,000 volts for reliable spark across all cylinders, reducing misfires and improving fuel economy.
- Cost-Effective Reliability: Delivers factory-level performance at a fraction of dealer prices, backed by Sierra's reputation for quality aftermarket marine components.
- Easy Maintenance: Simple visual inspections and resistance checks keep it performing like new season after season.
Perfect Fit for Popular Mercury Outboards
This ignition coil fits a range of Mercury and Mariner 4-stroke outboards, typically from 75HP to 115HP models in the mid-2000s era. Always cross-reference your engine's serial number to confirm, as it slots right into the ignition module housing for models requiring the 8M0077471 equivalent. No special tools needed—just disconnect the old coil, swap in the new one, and reconnect the wiring harness.
Quick Installation Steps
- Shut off the engine, disconnect the battery, and remove the cowling for access.
- Unplug the coil's electrical connector and loosen the mounting screws.
- Pull the spark plug wire boots straight off (twist gently if stuck).
- Install the Sierra 18-5158 in reverse order, torque to spec (usually 60-80 in-lbs), and test fire.
- Pro Tip: Apply dielectric grease to boots and terminals for extra corrosion protection.
Spotting and Preventing Ignition Coil Issues
Weak sparks lead to rough running, hard starting, or dead cylinders—hallmarks of a failing coil. Test yours with a multimeter: primary resistance should hover around 0.5-1.0 ohms, secondary 5,000-15,000 ohms. Common failures stem from cracked housings or water intrusion, but the Sierra 18-5158's sealed design laughs those off.
For longevity, rinse your engine after every saltwater run, inspect wires annually, and replace coils every 300-500 hours of operation. Pair it with fresh spark plugs for optimal results, transforming your outboard from sluggish to spirited.
Frequently Asked Questions
What engines is the Sierra 18-5158 ignition coil compatible with?
It serves as a direct replacement for Mercury Marine part 8M0077471, fitting various 75-115HP 4-stroke outboards. Verify with your engine's serial number for exact match.
How do I know if my ignition coil needs replacing?
Look for symptoms like misfires, rough idling, backfiring, or no-start conditions. Use a multimeter to check resistance values against OEM specs.
Is the Sierra 18-5158 as good as the original Mercury coil?
Yes, it's engineered to OEM standards with equivalent voltage output and durability, often exceeding in corrosion resistance for marine use.
Can I install the Sierra 18-5158 myself?
Absolutely—it's a straightforward DIY swap taking 15-30 minutes with basic tools. Disconnect the battery first for safety.
What makes this coil more durable in saltwater environments?
Epoxy encapsulation and high-grade insulators protect against moisture, salt, and vibration, extending service life over stock replacements.
Will this coil improve my engine's performance?
It restores factory spark strength, leading to smoother operation, better fuel efficiency, and reliable starts—especially if your old one was worn.
How often should I replace the ignition coil?
Every 300-500 engine hours or at the first sign of trouble. Regular maintenance like rinsing after use prolongs its life.
Save $46 when you buy the Sierra 18-5158 for only $105 from NVN Marine! Same day shipping before 3pm.
Sierra 18-5158 Technical Specifications
| Type: | |
|---|---|
| Vendor: |
Sierra Engine Parts |
| Weight: |
0.91 lb |
Sierra 18-5158 User Reviews
Sierra 18-5158 Shipping & Return
| Shipping Weight: |
0.91 lb |
|---|---|
| Box Sizes: |
3.00 (h) x 3.00 (w) x 4.00 (l) |
| Cubic Feet: |
36.0 |
| Returnable: |
Yes |
For detailed shipping policy please check our Shipping Policy and you can find our Return and Refund Policy here.