Thermostat Cover – Fits Yamaha 9.9–70HP & Mercury 8–60HP (Replaces 6H3-12413-00-1S, 8M0008243)
Thermostat Cover – Fits Yamaha 9.9–70HP & Mercury 8–60HP (Replaces 6H3-12413-00-1S, 8M0008243) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Thermostat Cover – Fits Yamaha 9.9–70HP & Mercury 8–60HP (Repla...
Product Details
This Thermostat Cover is designed for a wide range of Yamaha, Mercury/Mariner, and Parsun outboards. It fits Yamaha models from 9.9HP to 70HP (2-Stroke & 4-Stroke, 1984–2007), Mercury/Mariner models from 8HP to 60HP (2-Stroke & 4-Stroke, 1990–2007), and various Parsun 4-Stroke engines from 9.9HP to 60HP.
This component provides a direct replacement for Yamaha part numbers including 6H3-12413-00-1S, Mercury numbers like 8M0008243, and Parsun equivalents such as F15-07010021.
- Installs directly in place of the factory cover to secure the thermostat.
- Engineered for use in marine saltwater and freshwater environments.
- Package includes one thermostat cover.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yamaha | 6H3-12413-00-00 |
| Yamaha | 6H3-12413-00-94 |
| Yamaha | 6H3-12413-00-9M |
| Yamaha | 6H3-12413-00-1S |
| Mercury | 8250311 |
| Mercury | 825031C |
| Mercury | 857080 |
| Mercury | 8M0008243 |
| Mercury | 8M0188835 |
| Parsun | F15-07010021 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
Yamaha: Fits a wide variety of 2-stroke and 4-stroke models from 1984 onwards. Check your specific engine model and year against the list.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | F15A (66M) | 15 | 4-Stroke | 1998–2001 | 6H3-12413-00-1S | Multiple variants incl. 010, 020, 050, 060, 080, etc. |
| Yamaha | F20, F25 | 20, 25 | 4-Stroke | 1998–2008 | 6H3-12413-00-1S | F20 & F25 2-cylinder models |
| Yamaha | 25, 30HP | 25, 30 | 2-Stroke | 1984–2001 | 6H3-12413-00-1S | Various models including J/E & D/E variants |
| Yamaha | F30, F40 | 30, 40 | 4-Stroke | 2001 | 6H3-12413-00-1S | Includes variants B, ERA, BEDL, etc. |
| Yamaha | 40, 50HP | 40, 50 | 2-Stroke | Up to 2001 | 6H3-12413-00-1S | Various models |
| Yamaha | F45A | 45 | 4-Stroke | 1996–1998 | 6H3-12413-00-1S | Models 62Y |
| Yamaha | 50G/GEO/GETO | 50 | 2-Stroke | 1993–2001 | 6H3-12413-00-1S | 62F series models |
| Yamaha | F50A | 50 | 4-Stroke | 1995–2001 | 6H3-12413-00-1S | 62Y series models |
| Yamaha | 60F | 60 | 2-Stroke | 1984–1998 | 6H3-12413-00-1S | 6H2 series, multiple variants |
| Yamaha | 70B | 70 | 2-Stroke | 1984–2001 | 6H3-12413-00-1S | 6H3 series, multiple variants |
Mercury/Mariner: Broad compatibility with 2-stroke and 4-stroke engines produced up to 2007. This includes Bodensee and BigFoot variants.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | 8-9.9HP | 8, 9.9 | 4-Stroke | 1990–2007 | 8M0008243 | Models including Bodensee (OP086824-OP4000999) |
| Mercury | 13.5-15HP | 13.5, 15 | 4-Stroke | 1998–2007 | 8M0008243 | Models including S/N 9973100+ |
| Mercury | 25-70HP | 25-70 | 2 & 4-Stroke | Up to 2007 | 8M0008243 | Various models |
| Mariner | 8-9.9HP | 8, 9.9 | 4-Stroke | 1990–2007 | 8M0008243 | Models including Bodensee variants |
| Mariner | 9.9 BigFoot, 15-20HP | 9.9, 15, 20 | 4-Stroke | 2005–2007 | 8M0008243 | Big Foot models from 2005, 15/20 from 2007 |
| Mariner | 25-70HP | 25-70 | 2 & 4-Stroke | Up to 2007 | 8M0008243 | Various models |
Parsun: Compatible with many Parsun 4-stroke models. Refer to your service manual for part number F15-07010021.
| Brand | Model | Rated HP | Stroke | OEM Part No. | Notes |
|---|---|---|---|---|---|
| Parsun | F9.9, F13.5, F15 | 9.9, 13.5, 15 | 4-Stroke | F15-07010021 | Cylinder & Crankcase components |
| Parsun | F20, F25 | 20, 25 | 4-Stroke | F15-07010021 | Cylinder & Crankcase components |
| Parsun | F40 | 40 | 4-Stroke | F15-07010021 | Crankcase components |
| Parsun | F50, F60 | 50, 60 | 4-Stroke | F15-07010021 | Crankcase components |
Technical Specs
- Product Type
- Thermostat Cover
- Installation
- Direct replacement
- Fuel Type
- Gasoline
- Housing Material
- Aluminum
- Housing Color
- Silver/Gray
- Dimensions
- 5.0" L x 5.5" W x 1.5" H
- Fitting Type
- Direct bolt-on
- Primary Function
- Used to cover and secure thermostat in cooling system
What’s in the Box
- 1 x Thermostat Cover (6H3-12413-00-1S/8M0008243)
Installation Notes
- Ensure the engine is completely cool and disconnected from the battery.
- Locate the thermostat housing on the engine block. Place a rag underneath to catch any coolant spillage.
- Carefully remove the bolts securing the old thermostat cover.
- Remove the old cover and thermostat. Note the orientation of the thermostat.
- Clean both the engine block and new cover mating surfaces thoroughly, removing any old gasket material or corrosion.
- Install the new thermostat (if replacing) and place the new cover and gasket (not included) into position.
- Hand-tighten the bolts, then torque them to the manufacturer's specified values in a crisscross pattern. Do not overtighten.
- Reconnect the battery, start the engine, and check for leaks around the cover once the engine reaches operating temperature.
Troubleshooting & FAQ
How do I know if my thermostat cover is failing?
Signs of a failing thermostat cover include visible cracks, corrosion, or pitting on the housing; persistent coolant leaks from the gasket seal even after replacement; and warping that prevents a flush fit against the engine block.
Is a gasket included with this cover?
This part is sold as the cover only. The corresponding thermostat gasket must be purchased separately to ensure a proper seal during installation. Always use a new gasket when replacing the cover.
Can I reuse my old bolts?
It is generally recommended to use new bolts, especially if the old ones show any signs of corrosion, rust, or thread damage. Reusing compromised bolts can lead to improper torque and potential leaks.
What happens if the thermostat cover is not sealed correctly?
An improper seal can cause coolant to leak, leading to engine overheating, poor performance, and potential long-term damage. It can also allow air to enter the cooling system, reducing its efficiency.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost?
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns?
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
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