Mercury MerCruiser OEM Engine Gasket – 27-8M0150304

Mercury MerCruiser OEM Engine Gasket – 27-8M0150304

Part Number: 8M0150304 (full catalog number: 27-8M0150304)
Brand: Mercury Marine / Quicksilver
Official Product Type: Engine Gasket – OEM Powerhead/Engine Assembly
System: Engine Sealing – Powerhead / Engine Assembly
Mercury Prefix: 27- series (Mercury engine/powerhead gasket designation)

About This Part

This is a genuine Mercury OEM engine gasket for MerCruiser marine engines. The 27- prefix in Mercury’s part numbering system designates powerhead and engine assembly gaskets — components that seal critical engine joints such as cylinder heads, intake and exhaust manifolds, and major engine block assemblies. At this price point, this is a significant engine gasket, not a minor accessory seal. OEM gaskets use factory-spec materials, correct thickness, and precise die-cut geometry to ensure a lasting, leak-free seal that aftermarket alternatives frequently cannot match on marine engines.

Compatible Applications

• Mercury MerCruiser engines where part number 27-8M0150304 appears on the engine parts diagram
• Verify fitment using your engine model number and serial number against the Mercury MerCruiser parts diagram before ordering

Engine gasket fitment is highly specific to engine family, displacement, and serial number range. Always confirm this part number against the Mercury parts diagram for your exact engine model and serial number before ordering.

Serial Number / Fitment Note

Locate your MerCruiser engine serial number on the engine block tag or flame arrestor decal. Cross-reference this number against the Mercury MerCruiser parts diagram for your engine model to confirm 27-8M0150304 is the correct gasket for your assembly and location. Engine gaskets can vary between otherwise similar engines depending on displacement, head configuration, and production serial range.

System & Diagram Position

This part is found in the Engine / Powerhead section of the Mercury MerCruiser parts diagram under the 27- gasket series. Confirm the exact diagram position (cylinder head, intake manifold, exhaust manifold, or other engine joint) for your specific engine model before ordering. Adjacent parts in the same diagram section typically include related gaskets, seals, head bolts, and fasteners that should be inspected or replaced at the same time.

When to Replace

• Any time the sealed joint is disassembled — gaskets are single-use components and must never be reused
• Coolant or oil leaks at the engine joint this gasket seals
• Overheating events that may have warped the sealing surface or blown the gasket
• Engine rebuild or top-end service requiring disassembly of the sealed assembly
• White exhaust smoke or coolant loss indicating a compromised head or manifold seal

Installation Notes

• Gaskets are single-use — always install a new gasket; never reuse the old one
• Clean all mating surfaces thoroughly before installation — old gasket material or sealant residue will cause leaks
• Inspect the mating surfaces for warping, scoring, or corrosion before reassembly; a damaged surface will cause a new gasket to fail
• Replace all gaskets and seals disturbed during disassembly, not just the failed one
• Follow the Mercury MerCruiser service manual for the correct tightening sequence and torque specification — engine gaskets require precise torque to seal correctly
• Some engine gaskets require a specific sealant or are dry-fit only — confirm in the service manual before applying any sealant

Related Parts

• Mercury MerCruiser Gasket & Oil Seal Kit 8M0149926
• Mercury MerCruiser Quicksilver Gasket 8M0155369
• Quicksilver Intake Manifold & Valley Gasket Set 8.1L 496 MAG – 27-881633T01
• Mercury MerCruiser Quicksilver Cylinder Head Gasket Port 881631
• Mercury MerCruiser Quicksilver Gasket Exhaust Elbow Manifold 863726
• Mercury Quicksilver Exhaust Manifold Gasket 27-33395

Technical FAQ

Can I reuse this gasket if it looks undamaged?
No. Engine gaskets are single-use components. Once compressed under torque, the gasket material conforms to the surface and cannot re-seal reliably if disturbed. Always install a new gasket during any reassembly.

Do I need sealant with this gasket?
Follow the Mercury MerCruiser service manual for your specific engine and joint. Some engine gaskets are installed dry; others require a thin bead of approved sealant at specific locations. Using sealant where it isn’t specified — or omitting it where it is — can cause leaks or gasket failure.

How do I confirm this is the right gasket for my engine?
Use your engine model number and serial number to look up the Mercury MerCruiser parts diagram. The gasket part number and its location in the engine assembly will be shown in the diagram. If you’re unsure, contact us with your serial number and we can help identify the correct part.

What if my engine has overheated — do I need to check the mating surface?
Yes. Overheating can warp cylinder heads and manifolds. Before installing a new gasket, have the mating surface checked for flatness with a straightedge. A warped surface will cause a new gasket to fail regardless of quality.

Parts Desk Insights

Best use case: This gasket is the right call for a MerCruiser engine rebuild, top-end service, or any repair that requires disassembly of the engine joint it seals. At this price point it’s a major engine gasket — the kind of part that anchors a significant service job. Ordering it alongside related seals, fasteners, and any other gaskets disturbed during the same service is always the right approach.

Common mistakes: The most frequent error is ordering a gasket by engine displacement or model name alone without confirming the serial number — Mercury used different gasket specifications across production runs of the same engine. A second common mistake is skipping a surface flatness check after an overheating event and installing a new gasket on a warped surface, which leads to an immediate comeback. Also watch for customers who order only the failed gasket and skip adjacent seals that were disturbed during disassembly — always recommend a complete reseal of everything opened during the job.