804080-804080001 Mercury Standard Exhaust Valve | Genuine Used Part

🔧 Product Description

Genuine Mercury Cooling-System Pressure Control Valve - Part Number: 804080001

A genuine Mercury and Mariner cooling-system pressure-control valve for selected 75HP to 115HP four-stroke outboards.

This component is commonly known as the cooling-water poppet valve or pressure-relief valve. It is not an engine exhaust valve.

The valve opens as cooling-system pressure rises, allowing additional water to bypass through the engine cooling passages at higher operating speeds. It closes as pressure falls to maintain sufficient cooling-water pressure at idle and low speed.

Current Mercury part number 804080001 supersedes original part number 804080.

⚙️ Key Features

• Genuine Mercury / Mariner pressure-control valve
• Correct current part number 804080001
• Supersedes Mercury part number 804080
• Cooling-system poppet or pressure-relief valve
• Multiple OEM and branded aftermarket equivalents available

🚤 Compatibility

Commonly used on

• Yamaha-derived Mercury and Mariner inline four-cylinder four-stroke outboards
• Engine cooling systems using pressure valve 804080 or 804080001

Typically suits

• Mercury / Mariner 75HP FourStroke:
• Serial 0G960500 - 0T800999
• Serial 0T801000 - 1B226999
• Mercury / Mariner 75HP Bodensee FourStroke:
• Serial 0G960500 - 0T800999
• Serial 0T801000 - 1B226999
• Mercury 75HP EFI FourStroke:
• Serial 1B172291 - 1B366822
• Mercury 80HP EFI FourStroke:
• Serial 1B227000 - 1B366822
• Mercury / Mariner 90HP FourStroke:
• Serial 0G960500 - 0T800999
• Serial 0T801000 - 1B226999
• Mercury 90HP EFI FourStroke:
• Serial 1B172291 - 1B366822
• Mercury 100HP EFI FourStroke:
• Serial 1B227000 - 1B366822
• Mercury / Mariner 115HP EFI FourStroke:
• Serial 0T178500 - 0T800999
• Serial 0T801000 - 1B226999
• Serial 1B227000 - 1B366822
• HP Range: 75HP - 115HP
• Engine Type: Mercury / Mariner Yamaha-derived inline four-cylinder four-stroke outboard
• Year Range: Approximately 2000 - 2006

Cross-Brand Yamaha Applications

The equivalent Yamaha pressure-control valve design is also used on numerous Yamaha two-stroke and four-stroke engines. Those broader Yamaha applications do not automatically establish Mercury fitment and should be checked under the relevant Yamaha OEM number.

🔌 Function

The poppet valve regulates cooling-water pressure and bypass flow as engine speed changes.

At low speed, the valve remains closed or partially seated so water is retained within the cooling passages. As engine speed and water-pump pressure increase, the valve opens to allow additional cooling-water flow and prevent excessive system pressure.

⚠️ Common Signs of Failure

• Engine overheats at higher RPM
• Engine runs too cool because the valve is stuck open
• Overheating at idle because the valve does not seat
• Salt, sand or scale prevents free valve movement
• Valve rubber becomes distorted or hardened
• Cooling-water leakage from the valve cover or gasket
• Weak or inconsistent cooling-water discharge
• Temperature warning activates despite a serviceable water-pump impeller

🔄 Supersession & Cross Reference

OEM Supersession Chain

• 804080001 → Supersedes 804080
• 804080 earlier Mercury pressure-control valve

OEM / Cross-Brand Numbers

• Mercury: 804080001
• Mercury: 804080
• Yamaha: 60H-12416-00-00
• Yamaha: 6G5-12416-00-00
• Yamaha formatted numbers:
• 60H124160000
• 6G5124160000

Mercury identifies 804080001 as the functional replacement for 804080. Yamaha numbers 60H-12416-00-00 and 6G5-12416-00-00 cross-reference to the same poppet-valve design used in Yamaha-derived Mercury four-stroke engines.

OEM / Related Numbers

• Yamaha: 90480-20M05-00 related valve grommet
• Yamaha: 90501-16M11-00 related valve spring
• Yamaha: 6G5-11382-A1-00 related valve-cover gasket
• Yamaha: 6G5-11382-00-00 earlier gasket reference
• Related pressure-control valve cover and retaining hardware

Aftermarket / Verified Equivalents

• WSM: 785-200-01
• Recmar: replacement pressure-control / poppet valve for 804080 and 804080001
• Aftermarket 7517PK1 poppet-valve service kit:
• Poppet valve
• Spring
• Grommet
• Cover gasket
• Yamaha genuine updated valve: 60H-12416-00-00

The complete 7517PK1 kit is primarily catalogued for Yamaha applications. Its individual components cross-reference the Yamaha numbers associated with this valve, but the full kit should be checked against the exact Mercury valve-cover assembly before installation.

📦 Condition

• Genuine used part
• Removed from running engine where applicable
• In good working condition unless otherwise stated