Pump Housing Gasket – Fits Mercury Marine 9.9–20HP EFI Outboards (Replaces 27-8M0135804)

$5.30 $8.00

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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 high-quality Pump Housing Gasket ensures a reliable seal for the water pump on Mercury Marine 9.9–20HP EFI 2-cylinder 4-stroke outboards (2008 and newer). It is engineered to prevent leaks and maintain proper cooling system pressure, which is critical for engine health.

It serves as a direct replacement for Mercury/Quicksilver part numbers 27-8M0135804 and 8M0135804.

Designed for direct-replacement installation.
Meets or exceeds OEM specifications for fit and function.
Essential for routine water pump and impeller maintenance.

Part Number Matrix

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

Brand	Part Number
Mercury/Quicksilver	27-8M0135804
Mercury/Quicksilver	8M0135804

Engine & Model Compatibility

Confirm your engine model/year in the table below.

For Mercury Marine engines, it is crucial to verify your engine's serial number (S/N) falls within the specified range for correct fitment.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Mercury	EFI 2-cylinder	9.9	4-Stroke	2008–newer	8M0135804	from S/N 1R008146 & Up
Mercury	EFI 2-cylinder	10	4-Stroke	2008–newer	8M0135804	from S/N 0R833820 & Up
Mercury	EFI 2-cylinder	15	4-Stroke	2008–newer	8M0135804	from S/N 0R833820 & Up
Mercury	EFI 2-cylinder	20	4-Stroke	2008–newer	8M0135804	from S/N 0R833820 & Up
Mercury	EFI SeaPro 2-cylinder	15	4-Stroke	2008–newer	8M0135804	from S/N 0R833820 & Up

Technical Specs

Product Type: Pump Housing Gasket
Installation: Direct Replacement
Dimensions: 10.0 × 10.0 × 1.0 in
Weight: 0.03 kg (0.07 lb)
Warranty: 1-Year Warranty against manufacturing defects

What’s in the Box

1 x GASKET, PUMP HOUSING (8M0135804)

Installation Notes

Disconnect the battery and ensure the engine is turned off and cool.
Access the lower unit and locate the water pump housing.
Carefully remove the bolts securing the housing and detach it to expose the old gasket.
Remove the old gasket and thoroughly clean both mating surfaces, ensuring they are free of old material and corrosion.
Position the new gasket correctly on the cleaned surface.
Reinstall the water pump housing, tightening bolts to the manufacturer's specified torque.
Reconnect the battery, start the engine in a safe water-supplied environment, and check for leaks around the housing.

Troubleshooting & FAQ

How do I know if this gasket fits my Mercury engine?

Fitment is model-specific. Please verify your engine's model, rated horsepower, and year against the compatibility chart. For Mercury engines, it is critical to also check that your motor's serial number falls within the specified range.

What are the signs of a failing pump housing gasket?

Common symptoms include visible water drips or leaks from the water pump area, engine overheating at idle or low speeds, or a weak water stream from the "telltale" outlet. These indicate a loss of sealing pressure.

Do I need to use sealant with this gasket?

Typically, this type of gasket is designed for a dry installation on clean, smooth surfaces. However, we always recommend consulting your engine's official service manual for specific procedures and sealant recommendations for your model.

How often should this gasket be replaced?

It is standard practice to replace the pump housing gasket any time the water pump impeller is replaced or the lower unit is serviced. This preventative maintenance ensures a reliable seal.

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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