Reed Block Gasket – Fits Mercury/Mariner 135-275 HP V6 (Replaces 27-657443)

$5.99

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Product Details

This aftermarket Reed Block Gasket is engineered for a precise fit on Mercury/Mariner 135-275 HP, 2.0L & 2.4L V6 outboard engines manufactured between 1976 and 1994. It creates a critical seal between the reed block and the engine housing, ensuring proper crankcase pressure and engine performance.

It serves as a direct cross-reference for Mercury part numbers 27-657443, 27-657442, 27-657441, and 27-65744, as well as popular aftermarket equivalents including Sierra 18-0129, GLM 9-60062, and WSM 516-25.

Creates a reliable seal between the reed block and its housing.
Constructed from durable composite to resist gasoline and oil.
Specifically designed for 2-stroke Mercury & Mariner V6 engines.

Part Number Matrix

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

Brand	Part Number	Notes
Mercury	27-657443	Current OEM part number.
Mercury	27-657442	Superseded by 27-657443.
Mercury	27-657441	Superseded by 27-657443.
Mercury	27-65744	Superseded by 27-657443.
Sierra	18-0129	Aftermarket interchange.
GLM	9-60062	Aftermarket interchange.
WSM	516-25	Aftermarket interchange.

Engine & Model Compatibility

Confirm your engine model/year in the table below.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Mercury	V6	250	2-Stroke	1989–1990	27-657443
Mercury	V6	275	2-Stroke	1989–1994	27-657443
Mercury	V6 3.125" Bore	135	2-Stroke	1986–1990	27-657443	2.0L displacement
Mercury	V6 3.125" Bore	150	2-Stroke	1978–1990	27-657443	2.0L displacement
Mercury	V6 3.125" Bore	175	2-Stroke	1976–1981	27-657443	2.0L displacement
Mercury	V6 3.125" Bore XR2	150	2-Stroke	1986–1988	27-657443	2.0L displacement
Mercury	V6 3.375" Bore	175	2-Stroke	1981–1982	27-657443	2.4L displacement
Mercury	V6 3.375" Bore	200	2-Stroke	1978–1982	27-657443	2.4L displacement
Mercury	V6 3.375" Chrome Bore	175	2-Stroke	1983–1990	27-657443	2.4L displacement
Mercury	V6 3.375" Chrome Bore	200	2-Stroke	1982–1988	27-657443	2.4L displacement
Mercury	V6 3.375" Steel Bore XR-4	150	2-Stroke	1988–1990	27-657443	2.4L displacement

Technical Specs

Product Type: Reed Block Gasket
Installation Location: Between reed block and housing
Fuel Type: Gasoline
Material: Composite/Paper Gasket Material
Product Dimensions: 6.0 in x 7.5 in x 1.13 in
Weight: ~0.02 kg (0.04 lb)
Fitment Detail: Engine-specific fitment for specified Mercury V6 models

What’s in the Box

1 x Reed Block Gasket (Replaces 27-657443)

Installation Notes

Ensure the engine is off, cool, and disconnected from the battery.
Relieve any pressure from the fuel system according to your engine's service manual.
Remove the engine cowling and any components blocking access to the reed block housing.
Carefully detach the reed block assembly from the engine block.
Remove the old gasket and thoroughly clean both mating surfaces. Use a plastic scraper to avoid gouging the metal.
Confirm the surfaces are completely free of old gasket material, sealant, oil, and debris.
Position the new gasket, ensuring correct orientation with all bolt holes and passages aligned.
Re-install the reed block assembly. Tighten the fasteners in the sequence and to the torque value specified by the manufacturer.
Reassemble all components removed earlier.
Reconnect the battery, start the engine, and carefully inspect for any fuel or air leaks around the gasket.

Troubleshooting & FAQ

How do I confirm this gasket fits my Mercury engine?

This gasket fits a wide range of Mercury/Mariner 135–275 HP V6 outboards from 1976–1994. The best way to ensure a match is to verify your engine's model and year in the compatibility chart on this page. Also, cross-reference your existing part number with the equivalents in our Part Number Matrix.

Where is this gasket installed?

The reed block gasket is installed between the reed block and the crankcase (housing), creating a seal that is essential for proper engine compression and performance.

What are the signs of a failing reed block gasket?

Common symptoms include a rough idle, difficulty starting, loss of power, backfiring ("sneezing") through the carburetor, and increased fuel consumption. A faulty seal can disrupt the air/fuel mixture and crankcase pressure.

How often does this gasket need to be replaced?

Reed block gaskets do not have a fixed replacement interval. They should be replaced whenever the reed block assembly is removed for service or if symptoms of a leak appear.

What is this gasket made from?

It is constructed from a high-quality composite/paper gasket material designed to withstand exposure to fuel, oil, and heat in a marine environment.

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 vs 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

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