SKU: 80386256688

27-804908A00 Gasket Set Lower Unit Kit for Mercury 8HP 9.9HP 4-Stroke | JLM Marine

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Description

27-804908A00 Gasket Set Lower Unit Kit for Mercury 8HP 9.9HP 4-Stroke | JLM Marine27 804908A00 Gasket Set Lower Unit Kit for Mercury 8HP 9. 9HP 4 Stroke JLM Marine This Lower Unit Gasket Set is engineered to deliver a perfect fit and reliable performance for Mercury 8HP and 9. 9HP 4 stroke outboard engines. Designed as a direct replacement for OEM seal kits, it ensures a seamless installation and leak free operation for your lower unit assembly. This kit directly replaces Mercury part numbers 27 804908A00, 27 8M0082883, 27

27-804908A00 Gasket Set Lower Unit Kit for Mercury 8HP 9.9HP 4-Stroke | JLM Marine

This Lower Unit Gasket Set is engineered to deliver a perfect fit and reliable performance for Mercury 8HP and 9.9HP 4-stroke outboard engines. Designed as a direct replacement for OEM seal kits, it ensures a seamless installation and leak-free operation for your lower unit assembly.

This kit directly replaces Mercury part numbers 27-804908A00, 27-8M0082883, 27-8M0065830, 27-804908A02, and 27-8M0060176, providing broad compatibility across multiple Mercury lower unit configurations.

  • Comprehensive gasket and seal kit for complete lower unit service
  • Precision-engineered to OE specifications for reliable sealing
  • Fits Mercury 8/9.9 HP 4-stroke outboards (serial R042475 & up)

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket applications:

Brand Part Number Notes
Mercury 27-804908A00 Primary OEM reference
Mercury 27-8M0082883 Alternate OEM number
Mercury 27-8M0065830 Cross-reference
Mercury 27-804908A02 Cross-reference
Mercury 27-8M0060176 Cross-reference

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 Serial Range
Mercury Mariner 8 / 9.9 HP 4-Stroke R042475 & Up

Technical Specifications

Specification Value
Product Type Lower Unit Gasket & Seal Kit
Application Lower Unit Assembly
Compatibility Mercury 8HP / 9.9HP 4-Stroke Outboards
OEM Replacement Numbers 27-804908A00, 27-8M0082883, 27-8M0065830, 27-804908A02, 27-8M0060176

Package Contents

This kit includes:

  • 1× Lower Unit Seal Gasket Kit
  • The package contains all the parts shown in the product picture

Installation Guide

  1. Disconnect the outboard motor from the power source and allow it to cool completely.
  2. Drain all gear oil from the lower unit into an appropriate container.
  3. Remove the propeller, then unbolt and separate the lower unit from the mid-section housing.
  4. Carefully disassemble the lower unit components, noting the position of each seal and gasket.
  5. Clean all mating surfaces thoroughly, removing old gasket material and debris with a scraper and solvent.
  6. Inspect all surfaces for corrosion, warping, or damage that may prevent proper sealing.
  7. Install new gaskets and seals from this kit in the exact positions of the originals, ensuring correct orientation.
  8. Apply a thin coat of marine-grade grease to seals to aid installation and prevent damage during assembly.
  9. Reassemble the lower unit components, following your service manual's torque specifications for all fasteners.
  10. Reattach the lower unit to the mid-section, ensuring proper alignment and torquing all mounting bolts to spec.
  11. Refill the lower unit with the manufacturer-recommended gear oil through the fill port until it reaches the vent hole.
  12. Reinstall the propeller, run the engine briefly, then recheck the gear oil level and inspect for leaks.

Troubleshooting & FAQ

Q: How do I confirm this gasket set fits my Mercury outboard?
A: Check your engine's serial number (located on the mounting bracket) and confirm it is R042475 or higher for 8HP/9.9HP 4-stroke models. Cross-reference your current part number against the five OEM numbers listed above to ensure compatibility.

Q: How often should I replace the lower unit gaskets and seals?
A: Replace gaskets and seals whenever you perform lower unit service, disassembly for propeller shaft work, or if you notice gear oil leaks or milky oil indicating water intrusion. Most manufacturers recommend lower unit service every 100 hours or annually.

Q: What are the signs that my lower unit seals have failed?
A: Common symptoms include gear oil that appears milky (water contamination), visible oil leaks around the lower unit housing, difficulty shifting gears, unusual noise from the gearcase, or rapid gear oil loss between service intervals.

Q: Can I reuse the old gaskets if they look intact?
A: No, gaskets are designed for single use only. Even if they appear undamaged, they compress during initial installation and will not seal properly when reused, leading to leaks and potential water intrusion into the lower unit.

Q: Do I need any special tools to install this gasket set?
A: You'll need basic hand tools (sockets, wrenches, screwdrivers), a torque wrench, gasket scraper, marine-grade grease, and the appropriate gear oil. A service manual for your specific engine model is highly recommended for proper torque specifications and assembly procedures.

Q: What's the difference between OEM and aftermarket gasket sets?
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: 80386256688

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Reviewed in the United States on February 17, 2026
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Austin
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An engaging and accessible exploration of how computers really work. The author breaks down complex concepts into simple, relatable explanations, making topics like binary, logic gates, and basic circuits far less intimidating. For newcomers, it’s a great way to build a foundational understanding of computer theory with just a touch of electrical engineering. As someone with a technical background, I still found it entertaining; the examples and analogies added fresh ways to frame ideas I already knew. It’s the kind of book that can bridge the gap between “I use computers” and “I understand what’s happening under the hood.” Highly recommended for anyone curious about what makes hardware and software tick, whether you’re starting from scratch or just want a new perspective.
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Peter
Grantham, US
★★★★★ 5
CODE is the book you should get.
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The best book to enter the field. Grateful that Charles Petzold decided to write it, even happier this was one of the first books I picked up. Recommend to everyone wanting to become a programmer, or just interested in computers.
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Reviewed in the United States on January 12, 2026
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Michael Donoghue
Chelsea, US
★★★★★ 5
If you only buy one technical computer book, this is it
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Disclaimer: I owned the first edition for years and read it a dozen times, mainly for pleasure since it’s not only informative but also just enjoyable to read. I’m a professional software architect and have dozens of textbooks on computer science and engineering so I’ve been around the block. This is the kind of book I would buy all for all my friends (if I had more than a couple) and family members (if they were even slightly into computers, which they aren’t sadly). Petzold does an exceptional job at describing digital logic and guides you through building a conceptual CPU from very first principles. I think his bottom up approach is the way to go and has helped me understand complex topics in an extremely simple way. When I’m not reading fiction, this is my go to bedtime reading. The second edition has about 100 more pages than the first and some content has been completely reworked and it’s great. If you ever had even a passing interest in knowing how computers work at a very fundamental level, get this book!
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Yura
Phoenix, US
★★★★★ 4
First programmer?
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As an ardent reader of the past 1st edition, I was fairly excited to get the latest version. That is, until I encountered the history chapter of the new edition. For one thing, what I do NOT understand in this second edition is the newly added description of August Ada Byron (countless of Lovelace). The author claims it was Babbage who was the first programmer to design the engines, not Ada. I am not trying to start a futile argument here about who has more or fewer contributions, etc. What I am trying to assert here is that it is undisputed that Ada (unless the new evidence arises) left *the very first demonstration* of what this seemingly imaginary machine, which didn't even physically exist, was capable of through her program. Because Babbage designed the engine itself, that doesn't automatically put him in the position of a programmer (despite Babbage being a brilliant engineer/scientist and may have had a simple or detailed program in his mind). However, it was Ada who gave a definite touch to programming concepts that ultimately led to modern-day programming. Ada deserves more recognition than a mere "tutorial writer," and she is certainly entitled to the title she deserves. Other than that, like the previous edition, this book is a must-read for people who are from related/unrelated fields. I always loved the 1st edition, and I would do too with the 2nd. Still, I think history should always be approached with more care, particularly if matters have potential controversies.
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Reviewed in the United States on January 6, 2023

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