Mercury Quicksilver Exhaust Manifold Gasket 27-33395 | MerCruiser Small-Block V8 283 305 327 350 377

Exhaust Manifold Gasket for MerCruiser Small-Block GM V8 Engines

The Mercury Quicksilver 27-33395 is an OEM exhaust manifold gasket that seals the joint between the cylinder head exhaust ports and the exhaust manifold on compatible MerCruiser small-block GM V8 marine engines. A properly sealed manifold gasket keeps exhaust gases routed through the cooling water jacket and out of the engine compartment — critical for both performance and safety aboard.

This gasket uses a standard 4-bolt manifold port pattern and is approximately 1/16" thick. On V8 engines, manifold gaskets are typically replaced in pairs — one per side.

Part Information

• Part Number: 27-33395
• Short Reference: 33395
• Brand: Mercury / Quicksilver
• Official Product Type: Exhaust Manifold-to-Cylinder Head Port Gasket
• Barcode / UPC: 745061136557
• Related Set Reference: 27-33395A2 (pair / full set)
• Aftermarket Cross-References: Sierra Marine 18-4394, Sierra 18-0872, GLM Marine 39280, Mallory 9-61402, Fel-Pro 17420

Compatible Applications

• MerCruiser 283 CID small-block GM V8 marine engines
• MerCruiser 305 CID small-block GM V8 marine engines
• MerCruiser 327 CID small-block GM V8 marine engines
• MerCruiser 350 CID / 5.7L small-block GM V8 marine engines
• MerCruiser 377 CID small-block GM V8 marine engines

Fitment Note: Verify by engine serial number, cylinder head casting, exhaust manifold style, bolt pattern, and the Mercury parts diagram for your specific engine package. Exhaust gasket fitment can vary by manifold design and port shape even within the same displacement family.

System & Diagram Position

This gasket sits at the exhaust manifold-to-cylinder head interface — the sealing layer between each exhaust port on the cylinder head and the corresponding port on the exhaust manifold. In the MerCruiser engine diagram, it appears in the exhaust manifold section, one gasket per manifold (two total on a V8). The manifold routes exhaust gases through a water-cooled jacket before exiting through the exhaust elbow and transom.

Dimensions

• Bolt Pattern: Standard 4-bolt exhaust manifold pattern
• Approximate Thickness: 1/16" (1.6 mm)

When to Replace

• Exhaust ticking or popping sound at the manifold joint
• Visible soot, carbon deposits, or burn marks around the manifold flange
• Water staining or corrosion at the manifold-to-head joint
• Any time the exhaust manifold is removed for service or replacement
• Preventive replacement during a major engine service or overhaul

Service Interval

Exhaust manifold gaskets do not have a fixed replacement interval but should be inspected any time the manifold is removed or when exhaust leak symptoms appear. On older engines or those with significant heat cycling, proactive replacement during manifold service is good practice.

Installation Notes

• Clean both the cylinder head and manifold sealing surfaces thoroughly before installation — any debris or old gasket material will cause a leak
• Inspect the manifold face for warping, cracks, or corrosion; a warped manifold will not seal correctly regardless of gasket quality
• Check manifold bolt condition and replace any that are corroded or stretched
• Follow the Mercury service manual torque sequence and specification for manifold fasteners
• On V8 engines, replace both sides at the same time if either side shows age or leakage

Related Parts

• HGE Open Riser Gasket – MerCruiser V6 V8 (HGE-43781)
• Mercury Fuel Pump Gasket 27-34213
• Mercury Sea Water Pump Gasket 27-881603001
• Mercury MerCruiser Water Pump to Gear Housing Gasket 27-85610
• Mercury Quicksilver Lower Unit Seal Kit 26-33144A2

Technical FAQ

Q: Do I need to replace both sides on a V8?
A: Not always required, but strongly recommended. If one side has failed or is being disturbed, the opposite side has the same age and heat exposure. Replacing both at the same time avoids a repeat job shortly after.

Q: Can I reuse the exhaust manifold gasket after removing the manifold?
A: No. Once compressed and heat-cycled, the gasket should be replaced. Reusing an old gasket is a common cause of repeat exhaust leaks.

Q: What is the difference between 27-33395 and 27-33395A2?
A: The 27-33395 is a single gasket. The 27-33395A2 is the paired set (both sides for a V8). If you are doing both sides, ordering the A2 set may be more convenient.

Q: Will this gasket fit my exhaust riser or elbow?
A: This gasket seals the manifold-to-head joint only, not the riser or elbow connection. Riser and elbow gaskets are separate parts — see the HGE Open Riser Gasket for that application.

Parts Desk Insights

Best use case: This is the right gasket for any MerCruiser small-block V8 exhaust manifold removal — whether you're chasing an exhaust tick, replacing a corroded manifold, or doing a full engine service. It's an inexpensive part that should always be replaced rather than reused once the manifold is off.

Common mistakes: The most frequent error is ordering a single gasket for a V8 and then needing to order a second one mid-job. If both manifolds are coming off, order two (or the A2 set) upfront. A second common mistake is installing a new gasket on a warped manifold face — the gasket will fail quickly if the sealing surface isn't flat. Always check the manifold with a straightedge before reassembly.