Gasket – Fits Mercury/Mercruiser 9.9, 15, 18, 20 HP Outboards (Replaces 27-8M0075040)

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You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).

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Delivery and Shipping

Free standard shipping on all orders under 1 KG

If you have any questions, feel free to email us at info@sierramarines.com, and we’ll get back to you within 20–36 hours.

Product Details

This replacement Gasket – Fits Mercury/Mercruiser 9.9, 15, 18, 20 HP Outboards (Replaces 27-8M0075040) is designed for a precise fit on a range of Mercury/Mercruiser engines, covering both 2-Stroke and 4-Stroke applications. It ensures a reliable seal for optimal engine performance and longevity.

This part serves as a direct replacement for Mercury part numbers 27-8M0075040 and 27-855567002, offering an equivalent for interchange and cross-reference purposes.

Engine-specific fit ensures proper sealing.
Designed to withstand the marine environment.
This is a special order item.

Part Number Matrix

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

Brand	Part Number	Notes
Mercury	27-8M0075040
Mercury	27-855567002	Superseded by 27-8M0075040

Engine & Model Compatibility

Confirm your engine model/year in the table below.

This gasket is designed for specific Mercury/Mercruiser outboard models. Please verify your engine's rated horsepower and original part number before ordering.

Brand	Model	Rated HP	OEM Part No.	Notes
Mercury	Outboard	9.9	27-8M0075040
Mercury	Outboard	15	27-8M0075040
Mercury	Outboard	18	27-8M0075040
Mercury	Outboard	20	27-8M0075040
Mercury	Outboard		27-855567002	Superseded by 27-8M0075040

Technical Specs

Product Type: Gasket
Installation: Engine-specific
Dimensions: Length: 12.0 in, Width: 10.5 in, Height: 0.2 in
Weight: 0.009 kg (0.02 lb)
Other Technical Attributes: Special order item

What’s in the Box

1 x Gasket (27-8M0075040)

Installation Notes

Ensure the engine is off and cool. Disconnect the battery and any relevant power sources.
Drain any fluids (oil, coolant) as required by your service manual to prevent spills.
Carefully remove the component that the old gasket is sealing.
Thoroughly clean both mating surfaces, removing all traces of the old gasket material and any sealant, grime, or corrosion.
Inspect the cleaned surfaces for any warping or damage that could prevent a proper seal.
Position the new gasket correctly. Do not use sealant unless specified by the manufacturer.
Reinstall the component and tighten fasteners to the manufacturer's recommended torque specifications and sequence.
Refill any drained fluids and reconnect the battery. Start the engine and check for leaks.

Troubleshooting & FAQ

How do I confirm this gasket fits my specific engine model and year?

First, check the "Engine & Model Compatibility" table on this page. Cross-reference your engine's horsepower and model with the listed OEM part number. For absolute certainty, compare the part number stamped on your old gasket with 27-8M0075040 or 27-855567002.

What are common signs that my old gasket is failing?

Signs of a bad gasket include visible fluid leaks (oil, coolant), overheating, loss of compression, or milky/discolored engine oil. If you notice any of these symptoms, inspect the gasket and mating surfaces immediately.

Is any special sealant required for installing this gasket?

In most cases, this gasket is designed to be installed dry on clean, flat surfaces. Applying sealant can sometimes interfere with a proper seal. Always follow the specific instructions in your engine's service manual.

Why is this listed as a "special order item"?

A "special order" designation means the item may not be stocked in all our warehouses and might ship directly from the manufacturer, which can sometimes affect lead times. We will notify you of any delays.

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

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.

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