804081 Mercury Spring | Genuine Used Part

🔧 Product Description

Genuine Mercury Pressure-Control / Poppet Valve Spring - Part Number: 804081

A genuine Mercury cooling-system spring for the pressure-control or poppet-valve assembly on selected Yamaha-manufactured 75HP to 115HP four-stroke outboards.

The spring holds the pressure-control valve closed at lower cooling-system pressure and allows it to open as water pressure increases. Mercury 804081 cross-references Yamaha spring 90501-16M11-00.

⚙️ Key Features

• Genuine Mercury cooling-system spring
• Correct part number 804081
• Yamaha cross-reference 90501-16M11-00
• Calibrated for the pressure-control valve
• Used on Yamaha-built Mercury inline-four engines
• Maintains controlled cooling-water bypass operation

🚤 Compatibility

Documented on

• Mercury 75HP carburetted four-stroke, serial 0G960500-1B226999
• Mercury 75HP EFI four-stroke, serial 1B172291-1B366822
• Mercury 80HP EFI four-stroke, serial 1B227000-1B366822
• Mercury 90HP carburetted four-stroke, serial 0G960500-1B226999
• Mercury 90HP EFI four-stroke, serial 1B172291-1B366822
• Mercury 100HP EFI four-stroke, serial 1B227000-1B366822
• Mercury 115HP EFI four-stroke, serial 0T178500-1B366822
• Engine Type: Yamaha-manufactured Mercury inline-four four-stroke outboard
• HP Range: 75HP - 115HP

🔌 Function

The spring controls the opening pressure of the cooling-system relief valve. As pump pressure increases, the valve compresses the spring and opens a bypass passage.

⚠️ Common Signs of Failure

• Engine overheats at higher speed
• Engine runs too cool because the valve remains open
• Spring is corroded, broken or shortened
• Cooling pressure fluctuates
• Poppet valve sticks because the spring is distorted

🔄 Supersession & Cross Reference

OEM Supersession Chain

• 804081 current documented Mercury spring reference
• Yamaha 90501-16M11-00 direct platform cross-reference

OEM / Related Numbers

• Mercury 804081
• Yamaha 90501-16M11-00
• Mercury 804080 / 804080001 pressure-control valve
• Mercury 804082 related grommet
• Yamaha 67F-12435-A0-00 related poppet valve
• Yamaha 90480-20M05-00 related grommet
• Yamaha 6G5-12416-00-00 related valve component

Aftermarket / Verified Equivalents

• Recmar: REC90501-16M11
• Aftermarket Yamaha / Mercury poppet-valve service kits
• Generic calibrated pressure-control spring only when free length, wire diameter and spring rate match
• Genuine Yamaha 90501-16M11-00

📦 Condition

• Genuine used part
• Removed from running engine where applicable
• In good working condition unless otherwise stated
• Compare free length and tension before reuse