27-804680 Gasket Intake Manifold Reed for Mercury Mariner 6 Cyl 3.625 Bore 3L EFI 6 Cyl 3.6265 Bore 3.2L XS 6 Cyl 3.6265 Bore 3L Optimax 6 Cyl 3.6265 Bore 3L Pro XS | JLM Marine

Gasket Intake Manifold Reed – Fits Mercury Mariner 200-300 HP EFI/DFI/Optimax/XS Outboards

This Reed Block Gasket is engineered for Mercury and Mariner 6-cylinder outboard engines ranging from 200 to 300 HP, including 3.0L EFI, 3.0L Optimax, 3.2L XS, and Pro XS models. Designed to seal the reed valve assembly to the intake manifold, this gasket ensures optimal air-fuel delivery and prevents vacuum leaks that can compromise performance.

This gasket directly replaces OEM part numbers 27-804680, 804680, 27-841220, 27-850283, and 850283, providing a precise fit across multiple Mercury and Mariner engine configurations from 2000 to 2018.

• Essential seal for reed valve intake systems on high-performance outboards
• Compatible with EFI, DFI (Optimax), and Pro XS engine platforms
• Direct-fit replacement for faster, hassle-free installation

Part Number Cross-Reference

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

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.

Technical Specifications

Package Contents

This package includes the following components:

• 1 x Gasket Intake Manifold Reed

The package contains all the parts shown in the picture.

Installation Guide

1. Disconnect the battery and relieve any residual fuel pressure in the system. Ensure the engine is cool before beginning work.
2. Remove the engine cowling and locate the reed valve assembly on the intake manifold. Take note of the orientation of existing gaskets.
3. Unbolt and carefully remove the reed valve housing from the intake manifold. Set aside all fasteners in a safe place.
4. Peel off the old gasket material from both the reed block and intake manifold surfaces. Use a gasket scraper or plastic blade to avoid scratching machined surfaces.
5. Clean both mating surfaces thoroughly with a degreaser or carburetor cleaner. Allow all surfaces to dry completely before proceeding.
6. Position the new gasket over the intake manifold studs or alignment pins, ensuring it sits flat without wrinkles or tears.
7. Carefully align the reed valve housing onto the gasket and hand-thread all mounting bolts. Double-check alignment before tightening.
8. Torque the mounting bolts to the manufacturer's specification in a cross-pattern sequence to ensure even gasket compression.
9. Reconnect any fuel lines, vacuum hoses, or electrical connectors that were removed during disassembly.
10. Reinstall the engine cowling and reconnect the battery. Start the engine and check for vacuum leaks or unusual sounds.
11. Run the engine at idle for several minutes and inspect the gasket area for any fuel or air leaks.
12. Perform a brief test run under normal operating conditions to confirm proper performance and seal integrity.

Troubleshooting & FAQ

How do I confirm this gasket fits my specific Mercury or Mariner engine?
Cross-reference your engine's model, horsepower, and year range with the compatibility table above. You can also verify your original part number matches one of the OEM numbers listed (27-804680, 804680, 27-841220, 27-850283, or 850283).

How often should I replace the reed block gasket?
Replace the gasket whenever you service or remove the reed valve assembly, or if you notice performance issues such as rough idling, poor acceleration, or visible fuel/air leaks around the intake manifold.

What are the signs that this gasket has failed?
Common symptoms include loss of power, erratic idle, fuel smell near the engine, or hissing sounds from the intake area. Vacuum leaks caused by a deteriorated gasket will disrupt the air-fuel mixture and reduce engine efficiency.

Can I reuse the old gasket if it looks intact?
No. Gaskets are designed for one-time use and compress to form a seal. Reusing an old gasket can result in improper sealing, vacuum leaks, and potential engine damage.

Is this gasket compatible with both EFI and Optimax (DFI) engines?
Yes. This gasket is designed to fit Mercury 3.0L and 3.2L 6-cylinder engines across EFI, DFI (Optimax), XS, and Pro XS platforms from 2000 to 2018.

OEM vs. Aftermarket?
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.

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.