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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
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3H6010320
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346010320
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350020320
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5040066
8M0214960
853702
853702005
898101194
0777387
18-3676
18-7170
307239
312979
33504
3852071
508675
765604
777387
8M0214926
9-43026