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Mercury Outboard Parts
Shop Mercury outboard motor parts by system, including cooling, fuel delivery, electrical, internal engine components, lower unit parts, and routine service items. Browse OEM and replacement Mercury marine parts to support maintenance, repair, and rebuild projects.
Shop by System
- Complete Powerheads
- Control Cables & Boxes
- Cooling System
- Cowlings & Components
- Electrical System
- Engine Oil
- Engine Rebuild Kits
- Fuel & Carburetion System
- Intake System
- Internal Engine Components
- Lower Unit Components
- Oiling System
- Paints
- Service & Oil Change Kits
- Service Manuals
- Steering Systems
- Throttle Components
- Transom & Midsection
- Trim System
- Wizard Performance Parts
Common Mercury Outboard Model References
This category supports many popular Mercury outboards across a wide horsepower range. Always confirm your model and serial number for best fitment.
- Portable & Midrange: 2.5HP–60HP (2-stroke & FourStroke)
- Performance: Pro XS and EFI platforms (75HP–300HP)
- Direct Injection: Optimax models (75HP–250HP)
- Premium Offshore: Verado models (135HP–400HP)
- Commercial: SeaPro models (commonly 75HP–300HP)
Always confirm your exact horsepower, model year, and serial number to ensure proper part compatibility before ordering.
Pro Marine 130°F V6 Outboard Thermostat
Mercury & Mariner 2.5L / 3.0L EFI & DFI Thermostat
The Pro Marine 9004 thermostat is a replacement 130°F marine thermostat for select Mercury and Mariner 175HP-300HP EFI, DFI, OptiMax, Pro Max, and Pro XS outboards.
Designed for high-performance Mercury V6 applications, this thermostat helps maintain proper engine operating temperature for cooling system efficiency, engine protection, and dependable outboard performance.
Compatible Applications
| Horsepower Range | Engine Family | Engine Type | Application Notes |
|---|---|---|---|
| 175HP-200HP | Mercury V6 2.5L | EFI | Select EFI cooling system applications |
| 175HP-200HP | Mercury V6 2.5L | DFI / OptiMax | Select OptiMax thermostat applications |
| 200HP-300HP | Mercury V6 3.0L | EFI | Select EFI cooling systems |
| 200HP-300HP | Mercury V6 3.0L | DFI / OptiMax | Select DFI and OptiMax applications |
| 175HP-300HP | Mercury Pro Max | High Performance V6 | Select Pro Max cooling systems |
| 175HP-300HP | Mercury Pro XS | High Performance V6 | Select Pro XS applications |
| 175HP-300HP | Mariner V6 Outboards | EFI & DFI | Equivalent Mercury platform applications |
We also stock Pro Marine thermostat part number 9004P for the same Mercury and Mariner applications.
View Pro Marine Thermostat 9004P
OEM Part Numbers & Cross References
| Type | Part Number |
|---|---|
| Current Mercury OEM Number | 8M0057307 |
| Mercury Cross Reference | 885599 |
| Mercury Cross Reference | 885599002 |
| Mercury Cross Reference | 885599003 |
| Mercury Cross Reference | 885599004 |
| Mercury Cross Reference | 885599005 |
| Mercury Cross Reference | 8855991 |
| Pro Marine Part Number | 9004 |
What This Thermostat is Used For
This thermostat regulates cooling system water flow to help maintain proper engine operating temperature inside compatible Mercury and Mariner V6 outboards.
Proper thermostat operation is important for fuel efficiency, combustion quality, cooling system performance, and long-term engine durability.
A sticking or failed thermostat can contribute to overheating, inconsistent engine temperature, poor idle quality, or improper cooling system operation.
Thermostats are commonly replaced during cooling system maintenance, water pump service, or overheating diagnosis on high-performance Mercury outboards.
Key Features and Benefits
- Pro Marine replacement 130°F marine thermostat
- Fits select Mercury and Mariner 175HP-300HP V6 outboards
- Compatible with EFI, DFI, OptiMax, Pro Max, and Pro XS applications
- Replaces Mercury OEM 8M0057307 and 885599 series
- Supports proper engine operating temperature
- Helps maintain cooling system efficiency
- Designed for high-performance marine applications
- Excellent replacement for worn or sticking thermostats
Thermostat Details
- Brand: Pro Marine
- Part Number: 9004
- Temperature Rating: 130°F
- OEM Reference: 8M0057307
- Cross References: 885599, 885599002, 885599003, 885599004, 885599005, 8855991
- Applications: Mercury & Mariner 175HP-300HP V6 Outboards
- Engine Families: 2.5L & 3.0L V6
- Compatible Systems: EFI, DFI, OptiMax, Pro Max, Pro XS
- System: Cooling System
- Use: Engine temperature regulation
FAQ
What engines does this thermostat fit?
This thermostat fits select Mercury and Mariner 175HP-300HP EFI, DFI, OptiMax, Pro Max, and Pro XS V6 outboards using the listed OEM references.
What temperature is this thermostat?
This is a 130°F marine thermostat.
What OEM numbers does this replace?
This thermostat replaces Mercury OEM number 8M0057307 along with the 885599 series thermostat numbers.
When should a thermostat be replaced?
Thermostats are commonly replaced during cooling system maintenance, overheating diagnosis, or water pump service.
Do you offer another version of this thermostat?
Yes. We also stock alternate Pro Marine thermostat part number 9004P for compatible applications.
Dealer Discounts & Store Policies
Dealer / Marine Industry Discounts
Are you a marine dealer, technician, boat builder, or industry professional? We offer dealer pricing for qualified marine businesses.
Shipping Policy
- Free shipping on orders over $100 continental U.S.
- Orders ship via UPS, USPS, and FedEx.
- Orders received before 5:30 PM EST ship the same business day.
- Typical delivery time is 1–5 business days.
30-Day Return Policy
- Returns accepted within 30 days of delivery.
- Cooling system parts should be installed only after proper diagnosis and inspection.
- Items must be new, unused, and in original packaging.
- Return authorization is required before sending items back.
Need help with a return or order question?
Contact Us
Phone: 941-721-3000
Searchable Terms
9004, 8M0057307, 885599, 885599002, 885599003, 885599004, 885599005, 8855991, Mercury thermostat, Mercury 130 thermostat, Mercury OptiMax thermostat, Mercury Pro XS thermostat, Mercury Pro Max thermostat, Mercury 2.5L thermostat, Mercury 3.0L thermostat, Mercury V6 thermostat, Mariner thermostat, 130 degree marine thermostat, Pro Marine thermostat
8M0057307
885599
885599002
885599003
885599004
885599005
8855991