27803508 Mercury MerCruiser Gasket | Genuine Quicksilver OEM Part

🔧 Product Description

Genuine Quicksilver Cylinder Head Gasket - Part Number: 27-803508

A genuine Quicksilver cylinder head gasket for Mercury / Mariner 4HP, 5HP and 6HP four-stroke outboards. This gasket seals the cylinder head to the block and is replaced during cylinder head removal, top-end inspection or engine resealing.

⚙️ Key Features

• Genuine Quicksilver OEM cylinder head gasket

• Correct Mercury part number 27-803508

• Used on Mercury / Mariner 4HP, 5HP and 6HP four-stroke outboards

• Also cross-referenced with Tohatsu / Nissan small outboard gasket reference 3H6-01005-1

• Required replacement gasket when the cylinder head is removed

🔄 Supersession & Cross Reference

OEM Supersession Chain:

• 27-803508 current OEM service reference

OEM / Related Numbers:

• 27-803508

• 803508

• 27803508

Aftermarket / Verified Equivalents:

• Tohatsu / Nissan: 3H6-01005-1

🚤 Compatibility

Commonly used on:

• Mercury / Mariner 4-stroke small outboard cylinder head gasket applications

• 4HP, 5HP and 6HP cylinder block / cylinder head assemblies where 27-803508 is specified

Typically suits:

• Engine models:

• Mercury 4HP 4-stroke - serial 0P073456 to 0P400999

• Mercury 4HP 4-stroke - serial 0P401000 to 0R411837

• Mercury 4HP 4-stroke - serial 0R000001 to 0R067089

• Mercury 4HP 4-stroke - serial 0R067090 to 0R411837

• Mercury 4HP 4-stroke - serial 0R411838 and up

• Mercury 5HP 4-stroke - serial 0P073456 to 0P400999

• Mercury 5HP 4-stroke - serial 0P401000 to 0R411837

• Mercury 5HP 4-stroke - serial 0R000001 to 0R067089

• Mercury 5HP 4-stroke - serial 0R067090 to 0R411837

• Mercury 5HP 4-stroke - serial 0R411838 and up

• Mercury 5HP 4-stroke JCI - serial 0R560794 and up

• Mercury 5HP Propane - serial 0R936270 and up

• Mercury 6HP 4-stroke - serial 0P073456 to 0P400999

• Mercury 6HP 4-stroke - serial 0P401000 to 0R411837

• Mercury 6HP 4-stroke - serial 0R000001 to 0R067089

• Mercury 6HP 4-stroke - serial 0R067090 to 0R411837

• Mercury 6HP 4-stroke - serial 0R411838 and up

• HP Range: 4HP - 6HP

• Engine Type: Mercury / Mariner single-cylinder four-stroke outboard

• System Type: Cylinder head to block gasket

🔌 Function

The cylinder head gasket seals combustion pressure, cooling passages and oil-return areas between the cylinder head and engine block.

Common signs of failure:

• Compression loss

• Overheating

• Water or oil contamination

• Poor starting or rough running

• Gasket replacement required after cylinder head removal

📦 Condition

• Genuine Quicksilver part

• Brand new

• Supplied in original or equivalent packaging