SKU: 6866767392

300-8M0077471 184-0003 Ignition Coil for Mercury Optimax EFI | JLM Marine

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Description

300-8M0077471 184-0003 Ignition Coil for Mercury Optimax EFI | JLM MarineIgnition Coil for Mercury Optimax EFI Fits Mercury 2 Stroke & 4 Stroke Outboard Motors This aftermarket ignition coil is engineered for Mercury Optimax, Mercury EFI 2 Stroke, Mercury EFI 4 Stroke, and Mercury Racing engines ranging from 30 HP to 300 HP. It delivers reliable spark and performance across a wide range of applications, including recreational, Pro XS, and racing models. Direct replacement for Mercury OEM part numbers 300 8M0077471, 184

Ignition Coil for Mercury Optimax EFI – Fits Mercury 2-Stroke & 4-Stroke Outboard Motors

This aftermarket ignition coil is engineered for Mercury Optimax, Mercury EFI 2-Stroke, Mercury EFI 4-Stroke, and Mercury Racing engines ranging from 30 HP to 300 HP. It delivers reliable spark and performance across a wide range of applications, including recreational, Pro XS, and racing models.

Direct replacement for Mercury OEM part numbers 300-8M0077471, 184-0003, 300-879984T01, 339-879984A1, 339-879984T00, 879984T01, 8M00774714. Built to meet or exceed OEM specifications for dependable ignition across demanding marine conditions.

  • Compatible with Mercury Optimax, EFI 2-Stroke, EFI 4-Stroke, and Racing series engines
  • Direct-fit replacement – no modifications required
  • Meets or exceeds OEM performance standards

Part Number Cross-Reference

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

Brand Part Number
Mercury 300-8M0077471
Mercury 184-0003
Mercury 300-879984T01
Mercury 339-879984A1
Mercury 339-879984T00
Mercury 879984T01
Mercury 8M00774714

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
Mercury EFI 4-Stroke 30, 40, 50, 60 4-Stroke
Mercury Optimax 75, 90, 115, 125, 200, 225, 250 2-Stroke
Mercury Optimax Pro XS 115 Pro, 175 Pro, 200 Pro, 225 Pro, 250 Pro 2-Stroke
Mercury Optimax Racing 225 XS, 225 Sport XS, 250 XS, 250 Sport XS, 300 XS 2-Stroke
Mercury EFI 2-Stroke 150 (2.5 EFI), 175 (2.5 EFI), 200 (2.5 EFI), 200 (3.0 EFI), 225 (3.0 EFI), 250 (3.0 EFI) 2-Stroke
Mercury Racing EFI 2-Stroke 225X, 300X 2-Stroke

Technical Specifications

Specification Value
OEM Number 300-8M0077471, 184-0003
Type Ignition Coil
Compatibility Mercury Optimax, EFI 2-Stroke, EFI 4-Stroke, Racing series
Application Direct replacement for Mercury outboard motors

Package Contents

  • 1 × Ignition Coil

Installation Guide

  1. Disconnect the battery negative terminal to ensure safe working conditions. Confirm that the engine is off and cool to the touch.
  2. Locate the ignition coil on your Mercury outboard motor. Refer to your engine's service manual or parts diagram if needed.
  3. Disconnect the electrical connectors from the old ignition coil. Note the wire positions or take a photo for reference during reassembly.
  4. Remove the mounting bolts securing the old coil to the engine block. Keep the hardware for reinstallation unless new fasteners are provided.
  5. Remove the old ignition coil from the engine bay. Inspect the mounting area and clean any debris or corrosion.
  6. Position the new ignition coil in place, aligning the mounting holes with the engine block. Ensure proper orientation and seating.
  7. Install and tighten the mounting bolts to the manufacturer's recommended torque specification. Do not overtighten to avoid cracking the coil housing.
  8. Reconnect the electrical connectors to the new ignition coil, ensuring each wire is fully seated and secure. Double-check all connections against your reference photo.
  9. Reconnect the battery negative terminal. Ensure all tools and materials are clear of the engine bay.
  10. Start the engine and listen for smooth operation. Check for misfires, rough idle, or warning lights on the dashboard.
  11. Perform a test run at low speed, then gradually increase throttle to verify proper ignition performance. Monitor engine temperature and RPM stability.
  12. Inspect all connections after the test run to confirm there are no loose wires or vibration-related issues. Recheck mounting bolt torque if necessary.

Troubleshooting & FAQ

How do I confirm this ignition coil fits my Mercury engine?
Check the Compatible Engine Models table above for your engine's horsepower, stroke type, and series (Optimax, EFI, Pro XS, Racing). Cross-reference your existing coil's part number with the Part Number Cross-Reference table to ensure compatibility.

What are the signs that my ignition coil needs replacement?
Common symptoms include engine misfires, rough idling, difficulty starting, loss of power, poor fuel economy, and intermittent stalling. If you experience any of these issues, inspect the ignition coil for cracks, corrosion, or burnt connectors.

How often should I replace my ignition coil?
Ignition coils do not have a fixed service interval and are typically replaced only when they fail. Regular inspection during seasonal maintenance is recommended, especially if you operate in saltwater or harsh conditions.

Can I install this ignition coil myself, or do I need a professional?
If you have basic mechanical skills and tools, you can install this coil following the Installation Guide above. However, professional installation is recommended to ensure proper torque, electrical connections, and ignition timing verification.

What's the difference between this aftermarket coil and the OEM Mercury part?
This 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.

How fast do you ship and how much does it cost?
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.

What is your warranty and return policy?
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: 6866767392

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4.7 ★★★★★
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Justin Gatlin
San Leandro, US
★★★★★ 4
Nice shoes for about a year and a half
Size: 13 Wide, Color: Brown, Size: 13 Wide, Color: Brown
I bought these shoes about a year and a half ago and they are comfortable and look much more expensive than they actually are. Today, I noticed them starting to tear a little bit, but if I can replace them every 18 months for this price, it is probably still a better value than high end shoes. The grip is good for dress shoes and has held up well, and they are a good fit that does not cause blisters from excessive rubbing. I might not choose these if I need to wear them every day because of their lifespan, but for a once or twice a week pair of dress shoes, they are a good value.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 25, 2025
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Verified Purchase
Amazon Customer
Massapequa, US
★★★★★ 5
Runs big but great shoe!
Size: 12 Wide, Color: Black
Great looking shoe at a very good price! Runs big, I had to get the next size down for my son.
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Reviewed in the United States on May 17, 2026
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Verified Purchase
Butch M.
Carnegie, US
★★★★★ 5
Fantastic Shoe for the Price
Size: 9.5 Wide, Color: Wingtip Black
Okay, I’m used to spending big bucks on men’s dress shoes. I’m talking $300 plus for American made shoes. They are recraftable (resole-able) for another $100 each time. But since Covid, I don’t go to the office as often. One of my black dress shoes needs to be re-soled, and it will be. Just not now. So I ran into these shoes on Amazon. It’s hard to argue with the price. Literally 10% of what I have been paying. So, are these shoes 90% lower in quality? The short, simple answer is, surprisingly, no. Just the opposite. Upon receipt, I inspected them carefully and they looked pretty darned decent. I was looking for any excuse to plop them back in the box and return them. I couldn’t find anything. I appreciate that the leather upper is smooth and mildly shiny. This is a wing tip style shoe, so I’m impressed that the extensive stitching was evenly spaced. The leather detailing that I expect on a wing tip is also all there. Inside the shoe, it is lined from the toes all the way to the heel box… nice! And that leather feels surprisingly supple. That is something I would expect on a much more expensive shoe. But definitely not at this price point. Hmm. I even liked the wax laces they chose. They are a little thicker and have more than adequate length. The shoe’s eyelets have interior facing metal grommets to protect against stretching and tear out of the leather and helps protect the laces against friction wear, as they are tightened and loosened over time. Now having that detail, at this price point, has raised both of my eyebrows. Double hmm. Now I am really impressed. The only thing that I didn’t like was that the stitching—that joins the uppers to the sole—is white. I needed to polish these shoes anyway, so I figured I’d see what would happen if I put black polish on the stitching. I’m happy to say that the uppers shine up very nicely, to a high gloss. This was done with just a little bit of buffing, using a traditional horse hair bristled brush. And followed by a buffing cloth. Although I didn’t do it, the leather is smooth enough that I probably could have spit shined them. And those pesky white stitches on the top side of the soles? Well I’m happy to report that they are now definitely black. Turning the shoe over, I can visually see a lump where the shank is supposed to be. That’s a good thing. Not all shoes have a shank. It helps to support the arch. That’s another nice detail. I am expecting the shank to be plastic at this price point. So I am utterly shocked to report to you that a magnet sticks to the bottom of the shoe. That shank is steel! Now I am amazed! We’re talking mind blown, Purple smoke everywhere. Speaking of details, I was very surprised to see the nicely done wing tip detailing, from on top of the shoe, carried over to the bottom of the sole. Wow. I have never seen that before. That’s surprising. Now it is important to point out that the sole is some man made material. Definitely not leather. But that’s okay. Especially in the wet, leather wears out quickly, if you don’t wear rubber over shoes. One less thing to fuss about. The heel itself has a band/layer of rust brown material sandwiched between black layers. I wonder if that is a cork or bamboo material? Having walked in these shoes, on concrete and tile floors, last week, there is a noticeable level of cush, or give. They will definitely not to be confused with sneakers. But for dress shoes, this is a pleasant and surprising experience. The first day, I wore them at home, over the weekend and I’m glad I did that. They needed time to adjust to my feet. Any dress shoe that I have ever worn needs that. But after that, these shoes have been pleasant enough to walk around in at work. I’d have to say that these shoes give me at least 90% of what I would expect from my $300+ shoes for around 10% of the cost. In my estimation, at their current price point, they constitute an excellent deal. And especially if you are just breaking into the business world and need a good pair of interview shoes, these are definitely respectable… just be sure to put black polish on the white stitches. Oh, BTW, I have wider feet and I ordered the shoe wide. After the initial stretching, they fit nicely. So, in the final analysis, what do I think? I have to say, yes, these shoes definitely get my recommendation. Especially if price is a huge factor, then these shoes constitute an excellent deal.
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Reviewed in the United States on March 20, 2023
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Verified Purchase
Mark A Petrosino
Dallas, US
★★★★★ 5
Very Satisfied
Size: 10.5, Color: Black
Excellent Value . Very well made shoes . Shoes were true to size ! I am going to order in Brown also !
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Reviewed in the United States on June 9, 2026
N
Verified Purchase
Nikki
Massapequa, US
★★★★★ 5
Great dress shoe
Size: 10.5 Wide, Color: Black
Wow. Very impressed with these. Would purchase again. Comfortable enough for my teenage son, my husband and I very impressed with their look. Great for any special occasion. Ours appear to be all leather. Even the sole. These will last a lifetime if cared for.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 20, 2026

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