# 2778690002 Mercury MerCruiser Relief Valve Cover Gasket | Genuine Quicksilver OEM Part

🔧 Product Description

  

Genuine Quicksilver Relief Valve Cover Gasket - Part Number: 27-78690002

  

A genuine Quicksilver relief valve cover and plate gasket for Mercury V6 outboard cooling-system relief valve assemblies. This gasket seals the poppet / relief valve cover area to help maintain correct cooling-water pressure and prevent leakage at the cover joint.

  

⚙️ Key Features

  

• Genuine Quicksilver OEM gasket

• Correct Mercury part number 27-78690002

• Relief valve cover and plate gasket for Mercury V6 cooling systems

• Also referenced as 27-78690, 27-78690002 and 2778690002

• Cross-referenced with Sierra, Mallory and GLM gasket equivalents

  

🔄 Supersession & Cross Reference

  

OEM Supersession Chain:

  

• 27-78690002 current OEM service reference

• 27-78690 earlier / related OEM relief valve cover gasket reference

• 27-67624 earlier related relief valve cover gasket reference

  

OEM / Related Numbers:

  

• 27-78690002

• 78690002

• 2778690002

• 27-78690

• 78690

• 27-67624

• 67624

  

Aftermarket / Verified Equivalents:

  

• Sierra: 18-0936

• Mallory: 9-60057

• GLM: 31990

  

🚤 Compatibility

  

Commonly used on:

  

• Mercury V6 2.5L cooling-system relief valve / poppet valve cover assemblies

• Mercury DFI, EFI, Pro XS, Jet Drive and high-performance V6 outboard applications using 27-78690002

  

Typically suits:

  

• Engine models:

• Mercury 200 DFI Jet Drive powerhead - serial 0E435742 and up

• Mercury 200 DFI Jet Drive powerhead - serial 1B321662 to 1B321669

• Mercury 200 DFI Jet Drive pump - serial 0M964699 and up

• Mercury 200 DFI M2 Jet Drive pump - serial 0M965234 and up

• Mercury Magnum III - serial 0G960500 to 1B226999

• Mercury V-135 - serial 0G960500 to 0T178499

• 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-140 International - serial 0T178500 to 1B226999

• Mercury V-150 - serial 0G960500 to 1B226999

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

• Mercury V-150 EFI 2.5L - serial 1B227000 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-200 - serial 0G960500 to 1B226999

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

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

• Mercury XR-6 - serial 0G960500 to 1B226999

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

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

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

• Mercury 200XS SST - serial 1E050629 and up

• Mercury 225X EFI ProMax - serial 0T430254 to 0T819605

• Mercury 110 Jet 2.5L - serial 1B690542 and up

• Mercury 140 Jet - serial 0G960500 to 0T178499

• Mercury 150 Pro XS 2.5L - serial 1B690542 and up

• Mercury 175 Pro XS 2.5L - serial 1B516339 and up

  

• HP Range: commonly 110HP - 225HP where 27-78690002 is specified

• Engine Type: Mercury V6 2-stroke, EFI and DFI outboard cooling system

• System Type: Relief valve / poppet valve cover gasket

  

🔌 Function

  

The relief valve cover gasket seals the cooling-system relief valve cover and plate so the valve can regulate cooling-water pressure without leakage at the cover joint.

  

Common signs of failure:

  

• Water leaking from the relief valve cover area

• Cooling-water pressure loss

• Overheating at idle or under load

• Salt build-up around the poppet valve cover

• Gasket damage during relief valve service

  

📦 Condition

  

• Genuine Quicksilver part

• Brand new

• Supplied in original or equivalent packaging

## Details

- **Price:** 6.9 AUD
- **Vendor:** Quicksilver
- **Tags:** Quicksilver Marine Parts | Oils Service Kits & Engine Components

## Variants

| Variant | Price | Available |
|---------|-------|-----------|
| Default Title | 6.90 AUD | In stock |

## Images

- 2778690002 Mercury MerCruiser Relief Valve Cover Gasket | Genuine Quicksilver OEM Part

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> Source: [Sawley's Auto and Marine](www.sawleysautoandmarine.com.au/products/2778690002-mercury-mercruiser-relief-valve-cover-gasket-genuine-quicksilver-oem-part)
> Updated: 2026-05-17