27991764 Mercury MerCruiser Power Head Gasket | Genuine Quicksilver OEM Part

🔧 Product Description

Genuine Quicksilver Cylinder Block / Powerhead Base Gasket - Part Number: 27-991764

A genuine Quicksilver cylinder block / powerhead gasket used on selected Mercury and Mariner V6 2.5L 2-stroke, EFI, DFI / OptiMax and high-performance outboards. This gasket seals the cylinder block / powerhead to the mounting plate or exhaust plate assembly and is commonly required during powerhead removal.

⚙️ Key Features

• Genuine Quicksilver OEM powerhead gasket

• Correct Mercury part number 27-991764

• Cylinder block / powerhead base gasket

• Used on Mercury / Mariner V6 2.5L 2-stroke applications

• Commonly listed in complete powerhead and lower-unit gasket set components

🔄 Supersession & Cross Reference

OEM Supersession Chain:

• 27-991764 current OEM service reference

• 27-991764 related to earlier 27-991763 / 27-991762 gasket-family references where applicable

OEM / Related Numbers:

• 27-991764

• 991764

• 27991764

• 27-99176-4

• 27-991763

• 27-991762

• 27-78069 related earlier V6 powerhead base gasket family

• 27-991734 related driveshaft housing gasket

• 27-183076 related driveshaft housing plate gasket

Aftermarket / Verified Equivalents:

• Sierra: 18-2506-1

• WSM / aftermarket base gasket references for 27-991764 applications

🚤 Compatibility

Commonly used on:

• Mercury / Mariner V6 2.5L powerhead base / cylinder block gasket applications

• Mercury DFI / OptiMax and EFI powerhead gasket set components

Typically suits:

• Engine models:

• Mercury / Mariner 135HP V6 2.5L 2-stroke - serial 6618751 and up where 27-991764 is specified

• Mercury / Mariner 150HP V6 2.5L 2-stroke - serial 6618751 and up where 27-991764 is specified

• Mercury / Mariner 175HP V6 2.5L 2-stroke - serial 6618751 and up where 27-991764 is specified

• Mercury / Mariner 200HP V6 2.5L 2-stroke - serial 6618751 and up where 27-991764 is specified

• Mercury V-135 DFI 2.5L - serial 0T801000 to 1B226999

• Mercury V-135 DFI 2.5L - serial 1B227000 to 1B417701

• Mercury V-135 DFI 2.5L - serial 1B417702 and up

• Mercury V-150 DFI 2.5L - serial 0T801000 to 1B226999

• Mercury V-150 DFI 2.5L - serial 1B227000 to 1B417701

• Mercury V-150 DFI 2.5L - serial 1B417702 and up

• Mercury V-175 DFI 2.5L - serial 0T801000 to 1B226999

• Mercury V-175 DFI 2.5L - serial 1B227000 to 1B417701

• Mercury V-175 DFI 2.5L - serial 1B417702 and up

• Mercury V-150 EFI 2.5L - serial 0T801000 to 1B226999

• Mercury V-150 EFI 2.5L - serial 1B227000 and up

• Mercury V-200 EFI 2.5L - serial 0T801000 to 1B226999

• Mercury V-200 EFI 2.5L - serial 1B227000 and up

• Mercury 150 Pro XS 2.5L - serial 1B690542 to 2B535572

• Mercury 175 Pro XS 2.5L - serial 1B516339 to 2B535624

• Mercury 200XS DFI 2.5L - serial 0T818181 to 1E000796

• Mercury 200XS DFI 2.5L - serial 1E000797 to 1E002110

• Mercury 200XS ROS DFI 2.5L - serial 1E050852 and up

• Mercury 200XS SST - serial 1E050629 and up

• Mercury 110 / 140 Jet 2.5L V6 applications where 27-991764 is specified

• Mercury / Mariner V6 2.5L 135HP to 200HP 2-stroke outboards, commonly 1994-2014 service range where specified

• HP Range: commonly 110 Jet through 225HP V6 applications where specified

• Engine Type: Mercury / Mariner V6 2.5L 2-stroke, EFI, DFI / OptiMax and Racing outboard

• System Type: Cylinder block / powerhead base gasket

🔌 Function

The gasket seals the powerhead or cylinder block to the adapter / mounting plate, helping prevent exhaust leakage, water leakage and crankcase or midsection contamination at the base joint.

Common signs of failure:

• Water or exhaust leakage at powerhead base

• Overheating or cooling leakage after powerhead service

• Exhaust residue around mounting plate

• Gasket damaged during powerhead removal

• Required replacement whenever the powerhead is lifted

📦 Condition

• Genuine Quicksilver part

• Brand new

• Supplied in original or equivalent packaging