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Outboard Motor Parts | OEM & Aftermarket
Shop OEM and aftermarket outboard motor parts for Mercury, Yamaha, Suzuki, Honda, Johnson / Evinrude / E-TEC, Tohatsu / Nissan, and Chrysler / Force engines. Pro Marine USA carries parts for routine maintenance, troubleshooting, repair, and complete marine engine rebuilds.
Browse by outboard manufacturer or engine system, or use our OEM parts lookup to identify the correct part number before ordering. Find cooling, fuel, ignition, electrical, internal engine, lower unit, steering, trim, service kit, gasket, seal, and rebuild parts in one place.
Shop Outboard Parts by Manufacturer
Chrysler / Force Outboard Parts for Chrysler and Force outboard repair 
Honda Outboard Honda cooling, fuel, electrical, and engine parts 
Johnson / Evinrude / E-TEC Outboard Johnson, Evinrude, E-TEC, and OMC replacement parts 
Mercury Outboard Mercury and Mariner maintenance, repair, and rebuild parts 
Suzuki Outboard Suzuki service, lower unit, fuel, and engine parts 
Tohatsu / Nissan Outboard Tohatsu and Nissan outboard replacement parts 
Yamaha Outboard Yamaha maintenance, repair, lower unit, and rebuild parts Find the Correct Outboard Part
Not sure which part fits your engine? Start with the engine manufacturer, horsepower, model number, serial number, and year whenever available.
Our OEM parts lookup lets you view factory parts diagrams and identify the original part number for many popular outboard engines. Once you have the OEM number, search Pro Marine to find available OEM and aftermarket replacement options.
Use Our OEM Parts Lookup »Shop Outboard Parts by Engine System
Outboard engines use several interconnected systems. Select your manufacturer above to browse the exact categories available for your engine, including the following common repair and maintenance areas.
Common Outboard Problems and Where to Start
- Engine overheating: inspect the water pump, impeller, thermostat, pressure-control components, cooling passages, and engine anodes.
- Hard starting or rough idle: check fuel delivery, carburetor or injector operation, spark plugs, ignition components, filters, and intake sealing.
- Weak spark or no spark: test ignition coils, stators, switch boxes or ignition modules, sensors, wiring, grounds, and related electrical components.
- Low compression or poor power: inspect pistons, rings, cylinder condition, head and powerhead gaskets, bearings, and other internal engine components.
- Milky gear lube: inspect prop shaft, driveshaft, shift shaft, bearing carrier, and other lower unit seals for water intrusion.
- Lower unit or gearcase noise: inspect bearings, gears, clutch components, shafts, and gear lube condition before continued operation.
- Trim or steering problems: inspect hydraulic fluid level, seals, hoses, trim motors, pumps, steering cylinders, and mechanical connections.
Why Buy Outboard Parts from Pro Marine USA?
- OEM and aftermarket replacement options for major outboard engine brands.
- Marine engine parts for routine maintenance, professional repair, and complete rebuild projects.
- OEM diagram and part-number lookup tools to help identify the correct component before ordering.
- Dealer pricing available for qualified marine repair businesses and dealers.
- Large selection of service kits, engine parts, lower unit components, fuel system parts, electrical parts, steering, and rigging products.
- Same-day weekday shipping available on qualifying in-stock orders placed before the shipping cutoff.
OEM and Aftermarket Outboard Parts
OEM parts are supplied by the original engine manufacturer and are designed for the specific engine application. Aftermarket parts are replacement components produced by independent marine parts manufacturers and may provide additional availability or value for many common repairs.
Pro Marine carries both genuine OEM parts and quality aftermarket replacement parts for many outboard maintenance, repair, and rebuild applications. Always confirm fitment using the engine model, serial number, horsepower, year range, or OEM part number when available.
Frequently Asked Questions
How do I find the correct parts for my outboard motor?
Start by identifying the engine manufacturer, horsepower, model number, serial number, and year. Select the manufacturer above to browse by engine system, or use the OEM parts lookup to locate the original part number from a factory diagram.
Can I search Pro Marine by OEM part number?
Yes. If you already have the OEM part number, enter it into the Pro Marine site search to locate available OEM and aftermarket replacement options. If you do not know the part number, use the OEM parts lookup first.
What information should I have before ordering an outboard part?
Have the engine manufacturer, horsepower, model number, serial number, and year whenever possible. An OEM part number from the original component or parts diagram is especially helpful because visually similar parts may fit different engine families.
What is the difference between OEM and aftermarket outboard parts?
OEM parts come from the original engine manufacturer. Aftermarket parts are replacement components manufactured by other marine parts companies for compatible applications. Pro Marine carries both OEM and aftermarket options across many common outboard engine systems.
Are aftermarket outboard motor parts reliable?
Quality aftermarket marine parts are commonly used for maintenance, professional repair, and engine rebuilding. The best option depends on the application, manufacturer, availability, and customer preference.
Do you carry parts for older outboard motors?
Yes. Pro Marine carries parts for many older Mercury, Mariner, Johnson, Evinrude, Chrysler, Force, Yamaha, Honda, Suzuki, Nissan, and Tohatsu outboards. Availability varies by engine family and component.
What outboard parts are commonly replaced during routine maintenance?
Common maintenance items include engine oil, oil filters, fuel filters, spark plugs, water pump impellers, complete water pump kits, thermostats, gear lube, drain plug seals, anodes, and manufacturer-specific service kit components.
Fitment Tip: Outboard parts can vary by model, serial range, horsepower, and production year. Confirm the OEM part number or engine identification information whenever possible before ordering.
47929
57022
825101A2
85532
85532A1
859738T1
854512T
Pro Marine 130°F V6 Outboard Thermostat
Mercury & Mariner 2.5L / 3.0L EFI & DFI Thermostat
The Pro Marine 9004P 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 reliable 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 another Pro Marine replacement thermostat for compatible Mercury and Mariner applications.
View Alternate Pro Marine 130°F Thermostat
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 | 9004P |
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 critical 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: 9004P
- 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 9004 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
9004P, 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
884408A08
884408T05
884408T06
878231T2
OEM Mercury Thermostat Cover Kit
Mercury 3.0L EFI / DFI / OptiMax Thermostat Cover Assembly
This OEM Mercury thermostat cover kit is designed for select Mercury and Mariner 3.0L EFI, DFI, OptiMax, and Pro XS V6 outboards.
This cover kit helps restore proper thermostat sealing and cooling system performance on compatible Mercury 3.0L high-performance outboards.
Compatible Applications
| Horsepower Range | Engine Family | Engine Type | Application Notes |
|---|---|---|---|
| 200HP-225HP | Mercury / Mariner 3.0L V6 | EFI | Select 3.0L thermostat cover applications |
| 200HP-300HP | Mercury / Mariner 3.0L V6 | DFI / OptiMax | Select 3.0L DFI and OptiMax cooling systems |
| 225HP-300HP | Mercury Pro XS | 3.0L High Performance V6 | Select Pro XS thermostat cover applications |
This thermostat cover kit is commonly serviced together with the thermostat during cooling system maintenance.
View Pro Marine 130°F Thermostat
We also stock the alternate thermostat version:
View Pro Marine 130°F Thermostat 9004P
OEM Part Numbers & Cross References
| Type | Part Number |
|---|---|
| Mercury OEM Number | 885599A1 |
| Mercury OEM Cross Reference | 858856 |
| Pro Marine Item Number | 9004K |
What This Thermostat Cover Kit is Used For
This Mercury thermostat cover kit is used to secure and seal the thermostat assembly inside compatible Mercury 3.0L V6 outboards.
Proper thermostat cover sealing helps maintain correct cooling system pressure, water flow, and engine operating temperature.
Corrosion, damaged sealing surfaces, stripped hardware, or leaking gaskets can contribute to cooling system leaks and temperature regulation problems.
Thermostat cover kits are commonly replaced during thermostat service, cooling system rebuilds, or overheating diagnosis.
Key Features and Benefits
- OEM Mercury thermostat cover kit
- Fits select Mercury and Mariner 3.0L EFI, DFI, and OptiMax outboards
- Compatible with select Mercury Pro XS 3.0L applications
- Replaces Mercury OEM numbers 885599A1 and 858856
- Helps maintain proper thermostat sealing
- Supports proper cooling system operation
- Excellent replacement for corroded or leaking thermostat covers
- Designed for marine outboard cooling systems
Thermostat Cover Kit Details
- Brand: Mercury Marine
- Part Number: 9004K
- OEM References: 885599A1, 858856
- Applications: Mercury & Mariner 3.0L V6 Outboards
- Compatible Systems: EFI, DFI, OptiMax, Pro XS
- Engine Family: 3.0L V6
- System: Cooling System
- Use: Thermostat sealing and cover service
FAQ
What engines does this thermostat cover kit fit?
This kit fits select Mercury and Mariner 3.0L EFI, DFI, OptiMax, and Pro XS V6 outboards using the listed OEM references.
Is this an OEM Mercury part?
Yes. This is an OEM Mercury thermostat cover kit.
What OEM numbers does this replace?
This thermostat cover kit replaces Mercury OEM numbers 885599A1 and 858856.
Should the thermostat also be replaced during service?
In many cases yes. Thermostat covers and thermostats are commonly serviced together during cooling system maintenance.
What happens if the thermostat cover leaks?
A leaking or damaged thermostat cover can contribute to cooling system pressure loss, water leaks, and improper engine temperature regulation.
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
9004K, 885599A1, 858856, Mercury thermostat cover, Mercury thermostat housing, Mercury OptiMax thermostat cover, Mercury Pro XS thermostat cover, Mercury 3.0L thermostat housing, Mercury V6 thermostat cover, Mariner thermostat cover, thermostat cover kit, OEM Mercury thermostat cover kit, Mercury cooling system parts
885599A1
96233A2