Intake Manifold Reed Block Gasket – Fits Mercury Mariner 200HP 225HP 250HP 300HP EFI DFI Optimax (Replaces 27-804680, 804680, 27-841220, 27-850283, 850283)

Product Details

This Intake Manifold Reed Block Gasket is designed for Mercury Mariner 6-cylinder outboard engines, including 200HP, 225HP, 250HP, and 300HP models equipped with EFI, DFI, and Optimax fuel systems. Compatible with 3.0L and 3.2L displacement engines manufactured from 2000 through 2018, this gasket ensures a reliable seal between the reed block and intake manifold assembly.

This aftermarket replacement directly interchanges with Mercury OEM part numbers 27-804680, 804680, 27-841220, 27-850283, and 850283.

• Seals the reed block to intake manifold interface
• Compatible with EFI, DFI, and Optimax fuel injection systems
• Fits Mercury Pro XS and XS series engines

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

Engine & Model Compatibility

Confirm your engine model/year in the table below.

Technical Specs

Part Type

Intake Manifold Reed Block Gasket

Application

Mercury Mariner 200HP – 300HP EFI / DFI / Optimax

Engine Configuration

6-Cylinder

Displacement

3.0L / 3.2L

Fuel System

EFI, DFI, Optimax

OEM Reference

27-804680, 804680, 27-841220, 27-850283, 850283

What's in the Box

• 1 × Gasket

Installation Notes

1. Disconnect the battery and relieve fuel system pressure before beginning work.
2. Remove the intake manifold assembly to access the reed block.
3. Clean all mating surfaces thoroughly, removing old gasket material and residue.
4. Inspect the reed block and manifold for cracks, warping, or damage before reassembly.
5. Position the new gasket on the reed block, aligning all bolt holes.
6. Reinstall the intake manifold, torquing bolts to manufacturer specifications in a crisscross pattern.
7. Reconnect fuel lines and electrical connections securely.
8. Perform a pressure test or visual inspection for leaks before returning the engine to service.

Troubleshooting & FAQ

How do I know if my reed block gasket needs replacement?

Common signs include rough idling, loss of power, fuel odor, poor acceleration, or visible fuel leaks around the intake manifold. A failed gasket can cause air leaks that affect fuel mixture and engine performance.

Can I reuse the old gasket during reassembly?

No. Reed block gaskets are designed for single use and compress permanently when torqued. Reusing an old gasket will result in improper sealing and potential vacuum leaks.

Is this gasket compatible with both DFI and Optimax systems?

Yes. This gasket fits Mercury 3.0L and 3.2L engines with EFI, DFI, and Optimax fuel injection systems across the model years listed in the compatibility table.

What torque specification should I use for the intake manifold bolts?

Consult your Mercury service manual for exact torque specifications, as values vary by model year. Typically, intake manifold bolts require sequential torquing in a crisscross pattern to ensure even gasket compression.

Will this fit a 3.0L EFI 200HP from 2002?

Yes. This gasket is compatible with Mercury 6-cylinder 3.0L EFI 200HP, 225HP, and 250HP engines from 2002 through 2008.

OEM vs. Aftermarket?

This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.

Shipping speed & cost

We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.

Warranty & returns

Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.

Safety & Important Info

• Verify images/specifications against your original part. If anything differs—even if your model appears compatible—do not purchase.
• This is an aftermarket replacement, not an OEM component.
• Professional installation is recommended for safety and performance.

About Sea Sierra

• Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
• Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
• Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.