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OEM Mercury & Tohatsu Thermostat Gasket
Mercury & Tohatsu 4HP-30HP FourStroke Thermostat Cover Gasket
Genuine OEM thermostat cover gasket used on many Mercury and Tohatsu 4-stroke outboards ranging from 4HP through 30HP. This gasket helps create a proper seal between the thermostat housing and engine components during cooling system service.
Commonly replaced during thermostat maintenance, cooling system repairs, or preventative service on compatible Mercury, Mariner, Nissan, and Tohatsu outboards.
Compatible Mercury Applications
| Engine Range | Engine Type | Application Notes |
|---|---|---|
| 4HP / 5HP / 6HP | Mercury FourStroke | Select models and serial ranges |
| 8HP / 9.9HP | Mercury FourStroke | 209cc applications |
| 9.9HP ProKicker | Mercury FourStroke | Select ProKicker applications |
| 15HP / 20HP | Mercury Carbureted & EFI FourStroke | 2-cylinder applications |
| 25HP / 30HP | Mercury EFI FourStroke | 3-cylinder applications including Jet models |
| 15HP SeaPro | Mercury FourStroke | International SeaPro models |
Compatible Tohatsu Applications
| Engine Range | Engine Type | Application Notes |
|---|---|---|
| 8HP / 9.8HP | Tohatsu FourStroke | Select MFS models |
| 15HP / 20HP | Tohatsu FourStroke | Select EFI and carbureted models |
| 25HP / 30HP | Tohatsu FourStroke | Select EFI applications |
| Nissan Marine | FourStroke Outboards | Select rebadged Tohatsu applications |
OEM Part Numbers & Cross References
| Brand | Part Numbers |
|---|---|
| Mercury | 8M0214960, 853702, 853702005, 898101194 |
| Tohatsu | 3H6010320, 3H6010320M, 346010320, 346010320M, 350020320, 350020320M |
| Sierra | 18-60920 |
| Mallory | 9-60920 |
What This Thermostat Gasket is Used For
This OEM thermostat cover gasket is used to properly seal the thermostat housing during cooling system operation on compatible Mercury and Tohatsu outboards.
Replacing the gasket during thermostat service helps prevent coolant leaks, improper thermostat sealing, and cooling system pressure loss.
Thermostat gaskets are commonly replaced whenever the thermostat housing is removed for inspection, thermostat replacement, or routine maintenance.
Using the correct OEM gasket helps maintain proper fitment and sealing performance in harsh freshwater and saltwater marine environments.
Key Features and Benefits
- Genuine OEM Mercury and Tohatsu thermostat gasket
- Fits many 4HP-30HP FourStroke outboards
- Helps seal thermostat housing properly
- Supports cooling system reliability
- Common replacement during thermostat service
- Designed for marine cooling system environments
- OEM-quality fit and material construction
- Compatible with multiple Mercury and Tohatsu platforms
Thermostat Gasket Details
- Part Type: Thermostat Cover Gasket
- Primary OEM Number: 8M0214960
- Application: Mercury & Tohatsu FourStroke Outboards
- Horsepower Range: 4HP-30HP
- System: Engine Cooling System
- Use: Thermostat housing sealing
- Material: OEM marine gasket material
FAQ
What does this thermostat gasket fit?
This gasket fits many Mercury and Tohatsu-built 4-stroke outboards
ranging from 4HP through 30HP depending on model and serial range.
Should I replace the gasket when replacing the thermostat?
Yes. It is recommended to replace the thermostat gasket whenever the thermostat housing is removed to help ensure a proper seal.
Is this an OEM Mercury part?
Yes. This is a genuine OEM-style thermostat gasket cross-referenced to Mercury part number 8M0214960 and related superseded numbers.
Does this fit Tohatsu and Nissan outboards?
Yes. Many Mercury small FourStroke outboards are manufactured by Tohatsu, and this gasket also cross references to several Tohatsu and Nissan Marine part numbers.
Can a damaged thermostat gasket cause cooling issues?
Yes. A leaking or damaged gasket can contribute to improper thermostat operation, coolant leakage, or inconsistent engine temperatures.
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.
- 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
8M0214960, 853702, 853702005, 898101194, 3H6010320, 3H6010320M, 346010320, 346010320M, 350020320, 350020320M, thermostat gasket, Mercury thermostat gasket, Tohatsu thermostat gasket, Mercury 25HP thermostat gasket, Mercury 30HP thermostat gasket, Tohatsu thermostat cover gasket, Nissan Marine thermostat gasket, Sierra 18-60920
3H6010320
3H6010320M
346010320
346010320M
350020320
350020320M
5040066
8M0214960
853702
853702005
898101194
655-12414
655-12414-A1-00
655-12414-00-00
81031
81031M
0777387
18-3676
18-7170
307239
312979
33504
3852071
508675
765604
777387
8M0214926
9-43026
18-3628
18-3628-1
18-43175
19300-ZW9-003
19300-ZY3-023
3NV010300
3NV010300M
3R3010300
3R3010300M
3SA010300
3SA010300M
6G8-12411-00-00
6G8-12411-01-00
6G8-12411-02-00
6G8-12411-03-00
66M-12411-00-00
66M-12411-01-00
8M0119207
825212
825212A1
825212T02
825212001
855676
855676A1
855676002
855676003
855676005
18-3534
850055
850055001
9-43029
850055A1
850055A2
850055A1
850055A2
14586
9-43014
888988008
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
90390
90390A1
90390
90390A1