SKU: 76272577231

339-856991A1 339-850227 Ignition Coil for Mercury EFI Optimax Sport Jet | JLM Marine

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Description

339-856991A1 339-850227 Ignition Coil for Mercury EFI Optimax Sport Jet | JLM MarineIgnition Coil for Mercury EFI Optimax Sport Jet Fits 135 250 HP 6 Cylinder Engines This high quality aftermarket ignition coil is engineered for Mercury EFI, Optimax, and Sport Jet outboard engines. Designed to fit 6 cylinder 2. 5L and 3. 0L models from 1998 to 2006, it delivers reliable spark performance for 135 HP to 250 HP applications. This ignition coil directly replaces Mercury part numbers 339 856991A1, 339 850227, and Sierra part number 18

Ignition Coil for Mercury EFI Optimax Sport Jet – Fits 135-250 HP 6-Cylinder Engines

This high-quality aftermarket ignition coil is engineered for Mercury EFI, Optimax, and Sport Jet outboard engines. Designed to fit 6-cylinder 2.5L and 3.0L models from 1998 to 2006, it delivers reliable spark performance for 135 HP to 250 HP applications.

This ignition coil directly replaces Mercury part numbers 339-856991A1, 339-850227, and Sierra part number 18-5187. It meets or exceeds OEM specifications for reliable engine operation.

  • Direct-fit replacement for Mercury 6-cylinder EFI, Optimax, and Sport Jet engines
  • Meets or exceeds OEM performance standards
  • Package includes one complete ignition coil assembly

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Brand Part Number
Mercury 339-856991A1
Mercury 339-850227
Sierra 18-5187

Compatible Engine Models

Confirm your engine model/year in the table below. For Mercury owners, here's a guide to help you identify your engine's serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

Brand Model Rated HP Stroke Years
Mercury EFI 200 6 Cyl 2.5L 1998-2006
Mercury Optimax 135 6 Cyl 2.5L 1998-2006
Mercury Optimax 150 6 Cyl 2.5L 1998-2006
Mercury Optimax 175 6 Cyl 2.5L 2001-2006
Mercury EFI 225 6 Cyl 3.0L 1998-2006
Mercury Sport Jet 250 6 Cyl 3.0L 2002-2006

Technical Specifications

Specification Value
Part Type Ignition Coil
Application Mercury EFI, Optimax, Sport Jet Outboards
Engine Configuration 6-Cylinder
Displacement 2.5L / 3.0L
Compatible HP Range 135-250 HP
Quality Standard Meets or exceeds OEM specifications

Package Contents

  • 1 x Ignition Coil

Installation Guide

  1. Disconnect the negative battery cable to prevent electrical shock or short circuits.
  2. Locate the ignition coil on your engine; refer to your engine's service manual or parts diagram for exact positioning.
  3. Disconnect the spark plug wire from the old ignition coil. Label wires if multiple coils are present.
  4. Disconnect the electrical connector from the ignition coil.
  5. Remove the mounting bolts or screws securing the old ignition coil to the engine block.
  6. Carefully lift the old ignition coil away from the engine.
  7. Position the new ignition coil in the same location and align the mounting holes.
  8. Secure the new coil with the original mounting bolts or screws; tighten to manufacturer specifications.
  9. Reconnect the electrical connector firmly until it clicks into place.
  10. Attach the spark plug wire to the new ignition coil, ensuring a secure connection.
  11. Reconnect the negative battery cable.
  12. Start the engine and verify smooth operation with no misfires or rough idling.

Troubleshooting & FAQ

Q: How do I confirm this ignition coil fits my engine?
A: Check the Compatible Engine Models table above for your engine's brand, model, HP, and year range. You can also cross-reference the OEM part numbers (339-856991A1, 339-850227) with your original coil or consult your engine's parts diagram.

Q: What are the symptoms of a failing ignition coil?
A: Common signs include engine misfires, rough idling, difficulty starting, loss of power under load, and increased fuel consumption. If your engine runs poorly on certain cylinders, the ignition coil may be faulty.

Q: How often should I replace my ignition coil?
A: Ignition coils typically last several years under normal operating conditions. Replace them when you notice performance issues or during routine maintenance if they show signs of corrosion, cracking, or electrical failure.

Q: What is the difference between this aftermarket coil and the OEM version?
A: This aftermarket ignition coil is manufactured to meet or exceed OEM specifications using comparable materials and design. It provides reliable performance at a more competitive price point compared to OEM parts.

Q: Can I install this ignition coil myself?
A: If you have basic mechanical skills and tools, installation is straightforward. However, professional installation is recommended to ensure proper fitment, electrical connections, and optimal engine performance.

Q: Is this an OEM part or aftermarket?
A: This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

Q: How fast do you ship and how much does it cost?
A: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

Q: What is your warranty and return policy?
A: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

  • Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
  • This product is an aftermarket replacement part and is not an OEM component.
  • Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

  • Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
  • Fast Global Shipping: Free delivery worldwide in 5–15 days.
  • Direct from Manufacturer: Competitive pricing without compromising quality.
Shipping Notes
  • Free Standard Shipping on $100+ Orders to the USA.
  • Except Preorder products are shipped in 48 hours.
  • Delivery to the USA:
  1. Standard Shipping : 3-10 business days
  • If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
  • We offer a 30-day return/exchange service after receiving.
  • Final sale items are not eligible for returns or exchanges.
  • To process your return/exchange, please contact us at [email protected]
  • Please click here for more details>>> Return & Exchange Policy
SKU: 76272577231

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4.4 ★★★★★
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Chris T.
Draper, US
★★★★★ 1
Flattened out a little over a month or using it
Size: Sapphire Queen
Figured I would wait a month or 2 before leaving a review. At first. The pillow was great. Very comfortable. Held up nice. Nice and firm and gave great support. After a month. It started to flatten out. Had to re-fluff it only to have flatted out faster this time. Now no matter how many times I fluff it. It doesn’t give the proper support any longer. I’ve bought 2 of these and they are identical. So it can’t be just a fluke for the 2 i have. I’m regretting the purchase as the price was fair when I bought them. But not any longer as they are not the same.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on January 26, 2026
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Verified Purchase
Nick
Louisville, US
★★★★★ 5
Amazing - Stop Scrolling and Buy This Pillow
Size: Queen (Pack of 1), Color: White
I have been an Amazon customer ever since the very beginning, and this is my first review. Not because I haven’t purchased tons of amazing things (and a few bad ones), just never felt the need. However, I researched pillows for longer than I care to admit, and decided on this one. I’ve had it for about six months and absolutely love it. No lie, I genuinely look forward lying my big head on it after a long day. I am a side sleeper, but flip flop all around through the night and it’s great in every position. Pros: Stays nice and cool, which is soothing regardless of the time of year. Has a sort of quilted textured pattern on the zip up cover, gives it a luxury feel, that breaths nicely even when a pillow case is added. The fill is fully adjustable to your preference. I knew it came with extra filling but was worried it would not be enough. Wrong. It was very full and I ended up taking some out until it was perfect. It comes vacuum sealed and suggests it may take some time to fully take shape. However, I found it to be about 90% almost instantly and was sleeping on it a couple hours later. There was no unpleasant scent sometimes associated with memory foam items. The foam itself is very nice, a mix of what appears to be shredded and cotton candy cloud like. Very brilliant idea, as it is somehow supportive, soft and firm all at once. The affordability of this pillow compared to some of the others in this category can’t be overstated. Oh, and the packaging was very thoughtfully and securely done. If you are like me, an over thinker, I would suggest just taking this for a spin. It’s amazing. I’m not a bot, or working for the company. I’m just truly satisfied, love this pillow, and have been sleeping great.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on April 6, 2026
K
Verified Purchase
k25
Lexington, US
★★★★★ 5
It's the perfect pillow!
Size: Queen (Pack of 1), Color: White
I purchased this pillow specifically for its customizable fill feature, which allows you to add or remove stuffing to suit your personal comfort needs. Due to the unique curvature of my cervical spine—forward at the neck rather than backward—I require a soft, semi-flat pillow rather than one that is thick or firm. Additionally, I often experience ear discomfort by morning, so a gentler surface is essential. Upon adjusting the fill, I was pleasantly surprised by the generous amount of stuffing included. There was enough to fill an additional pillowcase, and I estimate it could easily create four to five more pillows. The ability to modify the pillow’s firmness at any time is an outstanding feature that makes it adaptable for a wide range of preferences and sleep styles. This pillow has exceeded my expectations in both comfort and versatility. I highly recommend it to anyone seeking a personalized sleep experience.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on February 1, 2026
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Verified Purchase
NC Coach
New York, US
★★★★★ 4
Good quality pillows overall
Size: King (Pack of 2), Color: White
Got a set of these for my wife and myself as we were struggling with our old pillows. These have some really good qualities and some things we'd like to see changed. First, the good: These are look and feel like they are high quality and made with good materials. The foam itself has a very nice feel to it. We love the fact they are adjustable to add or remove foam. They come with a pretty substantial amount already in the pillow. We appreciate the CertiPur certification. Now the improvements or changes we'd like to see: The foam, while feeling great, doesn't bounce back well if you scrunch your pillows, and so every day you have to fluff and reshape the pillow, moreso than some other memory foam pillows we've owned. One side of the pillow is cooled and you can feel that even through the pillow case, and that's a great thing. However, one side is not cooled and we'd have preferred if both sides were made of the cooling material. Overall, these are good pillows and we are not disappointed with the purchase. They are not, however, our perfect pillows (which do seem hard to find), and at some point in the future will probably make their way to the guest bedroom. We would rate them as some of the better pillows we've tried and feel most people would probably like them.
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Reviewed in the United States on December 19, 2025
A
Verified Purchase
Amazon Customer
Battle Creek, US
★★★★★ 5
Perfect Pillow
Size: Queen (Pack of 1), Color: White
These are the best pillows ever. You can adjust the firmness or softness to whatever you want. For years i used a soft latex pillow , which you cant get anymore. I will never use another pillow. I have purchased 6 of these after the first one. You pick your own comfort level. Best ever. No more neck aches.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 17, 2026

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