Head Gasket – Fits Mercury/Mercruiser 150HP 4-Stroke Outboard Motors (Replaces 27-8M6000366, 8M6000366)

$93.50

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Product Details

This replacement Head Gasket – Fits Mercury/Mercruiser 150HP 4-Stroke Outboard Motors is engineered for a precise seal on Mercury/Mercruiser 4-Stroke outboard engines from 135 to 150 HP, manufactured from 2011 to the present, matching specific serial number ranges for a guaranteed fit.

It serves as a direct interchange for Mercury part numbers 27-8M6000366 and 8M6000366, as well as Quicksilver 8M6000366.

Designed for engine repair and cylinder head replacement tasks.
Manufactured from materials meeting or exceeding OEM specifications.
Ensures a durable seal for gasoline-powered 4-stroke marine engines.

Part Number Matrix

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

Brand	Part Number
Mercury	27-8M6000366
Mercury	8M6000366
Quicksilver	8M6000366

Engine & Model Compatibility

Confirm your engine model/year in the table below.

This part is compatible with select Mercury, Mercruiser, and Mariner 4-stroke outboard models. Please verify your engine's serial number or model code falls within the specified ranges.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Mercury	150HP EFI	150	4-Stroke	2011–Present	27-8M6000366	Serial Number: 1B905505 & Up
Mercury	150HP EFI Pro XS	150	4-Stroke	2011–Present	27-8M6000366	Serial Number: 2B550139 & Up
Mercury	150HP EFI Sea Pro	150	4-Stroke	2011–Present	27-8M6000366	Serial Number: 2B139139 & Up
Mercury	135HP EFI	135	4-Stroke	2011–Present	27-8M6000366	Serial Number: 2B131942 & Up
Mariner	150HP	150	4-Stroke	2011	27-8M6000366	Models: 7150F24ZD, 7150F13ZD, 7150F23ZD

Technical Specs

Product Type: Cylinder Head Gasket
Installation: Engine Repair/Replacement
Fuel Type: Gasoline
Housing Material: OEM Specification Material
Dimensions: 55.0 cm × 19.0 cm × 0.3 cm
Weight: 0.18 kg (0.40 lbs)
Other Technical Attributes: Factory Original Equipment Manufacturer (OEM) Part

What’s in the Box

1 x Head Gasket (27-8M6000366/8M6000366)

Installation Notes

Disconnect the battery and drain the engine's cooling system completely.
Remove all interfering components such as the intake manifold, exhaust manifold, and valve cover.
Carefully remove the cylinder head bolts in the reverse order of the tightening sequence specified by the manufacturer.
Lift the cylinder head off the engine block and remove the old head gasket.
Thoroughly clean the mating surfaces of both the engine block and cylinder head, ensuring they are free of old gasket material, oil, and debris.
Position the new head gasket correctly on the engine block; do not use any sealant unless explicitly required.
Carefully place the cylinder head back onto the block.
Install new or inspected head bolts and torque them in the correct sequence and stages according to your engine's service manual.
Reassemble all previously removed components.
Refill the cooling system, reconnect the battery, and start the engine to check for any leaks.

Troubleshooting & FAQ

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

The most reliable method is to check your engine's serial number against the ranges provided in the "Engine & Model Compatibility" table. Your serial number is typically found on a tag on the transom bracket or on the engine block.

What are the common signs of a blown head gasket?

Symptoms include engine overheating, white smoke from the exhaust (coolant burning), a milky appearance in the engine oil (coolant mixing with oil), loss of compression, and poor engine performance.

Can I reuse my old head bolts for installation?

It is strongly recommended to use new head bolts, as many are torque-to-yield (TTY) bolts designed to stretch permanently upon first use. Reusing them can lead to improper clamping force and premature gasket failure.

Is any sealant required when installing this gasket?

Most modern head gaskets are designed to be installed dry. Unless the service manual for your specific engine explicitly calls for a sealant, do not apply any. Sealants can interfere with the gasket's ability to create a proper seal.

How is an aftermarket part different from the OEM version?

This is an aftermarket part, not a factory original. It is designed and manufactured to meet or exceed the performance specifications of the OEM part, offering a high-quality, cost-effective alternative.

What is the recommended replacement interval for a head gasket?

Head gaskets are not a routine maintenance item. They are typically replaced only when they fail or during a major engine overhaul.

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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