428853 Mercury Thermostat Cover | Genuine Used Part

🔧 Product Description

Genuine Mercury Thermostat and Pressure-Control Valve Cover - Part Number: 428853

A genuine used Mercury Marine cooling-system cover for selected 65 Jet to 125HP two-stroke outboard motors.

The cover seals the thermostat and pressure-control or poppet-valve cavity in the cylinder block. It allows the cooling system to regulate engine temperature at low speed and increase cooling-water flow at higher engine speeds.

⚙️ Key Features

• Genuine used Mercury cooling-system cover
• Original part number 428853
• Current replacement reference 8M0047619
• Used on three-cylinder and four-cylinder two-stroke engines
• Seals the thermostat and pressure-control valve cavity

🚤 Compatibility

Commonly used on

• Mercury and Mariner three-cylinder and four-cylinder two-stroke cooling systems
• Oil-injected cylinder-block thermostat assemblies

Typically suits

• Engine models:
• Mercury 65 Jet
• Mercury 80 Jet
• Mercury / Mariner 75HP three-cylinder
• Mercury / Mariner 90HP three-cylinder
• Mercury / Mariner 100HP four-cylinder
• Mercury / Mariner 115HP four-cylinder
• Mercury / Mariner 125HP four-cylinder
• USA serial groups including 0D283222 through 0G760299
• Later serial groups where the cover supersedes to 884297 or 8M0047619
• HP Range: 65 Jet / 75HP - 125HP
• Engine Type: Mercury / Mariner carburetted, oil-injected two-stroke outboard
• Year Range: Approximately late 1980s through the 2000s

🔌 Function

At lower engine speeds, the thermostat restricts coolant flow until the engine reaches operating temperature. At higher speeds, the pressure-control valve opens to permit additional cooling-water circulation.

⚠️ Common Signs of Failure

• Cooling water leaks around the cover
• Engine runs too hot or too cold
• Cover is warped or cracked
• Thermostat cavity is heavily corroded
• Poppet valve sticks because the cover is damaged or scaled
• Gasket repeatedly leaks
• Mounting-bolt threads are damaged

🔄 Supersession & Cross Reference

OEM Supersession Chain

• 8M0047619 → Supersedes 884297
• 884297 → Supersedes 428853
• 428853 → Related to earlier 428852 and 42885T references

OEM / Related Numbers

• 8M0047619
• 884297
• 428853
• 428852
• 42885T
• 42885-3
• Related thermostat as specified by engine serial number
• Related pressure-control valve, spring and seal
• Related cover gasket as specified by cylinder-block diagram

Aftermarket / Verified Equivalents

• Aftermarket replacement thermostat covers are available under references 8M0047619, 884297 and 428853

📦 Condition

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