Thermostat Housing Gasket – Fits MerCruiser 3.0L Marine Engines (Replaces 27-8146801, 27-814680)
Thermostat Housing Gasket – Fits MerCruiser 3.0L Marine Engines (Replaces 27-8146801, 27-814680) is backordered and will ship as soon as it is back in stock.
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Thermostat Housing Gasket – Fits MerCruiser 3.0L Marine Engines (Re...
Product Details
This replacement Thermostat Housing Gasket – Fits MerCruiser 3.0L Marine Engines (Replaces 27-8146801, 27-814680) is engineered for a precise seal on MerCruiser 3.0L (181 cu in) inline 4-cylinder engines, including MPI EC and TKS Plus models from 1987 to the present. It ensures proper thermostat function by preventing coolant leaks between the thermostat housing and the engine manifold.
It serves as a direct replacement for MerCruiser OEM part numbers 27-8146801, 27-814680, and 27-33680, offering a reliable fit and OEM-equivalent performance.
- Installation Location: Mounts directly between the thermostat housing and the intake manifold.
- Material: Composed of high-quality, non-metallic gasket material for a durable, leak-proof seal.
- Included Quantity: Each package contains one gasket.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Superseded By | Notes |
|---|---|---|---|
| MerCruiser | 27-33680 | 27-814680 | Original part number. |
| MerCruiser | 27-814680 | 27-8146801 | First supersession. |
| MerCruiser | 27-8146801 | Current part number. |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| MerCruiser | 3.0L GM 181 I/L4 (0L097000-0W301999) | 135 | 4-Stroke | 1987–1989 | 27-8146801 | Superseded 27-33680, 27-814680 |
| MerCruiser | 3.0L GM 181 I/L4 (0W302000-1A0019999) | 135 | 4-Stroke | 1990–1994 | 27-8146801 | Superseded 27-33680, 27-814680 |
| MerCruiser | 3.0L GM 181 I/L4 (1A002000-1A020543) | 135 | 4-Stroke | 1994–1998 | 27-8146801 | Superseded 27-33680, 27-814680 |
| MerCruiser | 3.0L GM 181 I/L4 (1A020544 & Up) | 135 | 4-Stroke | 1998-present | 27-8146801 | Superseded 27-33680, 27-814680 |
| MerCruiser | 3.0L MPI EC (1A072812 & Up) | 135 | 4-Stroke | 2003-present | 27-8146801 | Fuel injected variant |
| MerCruiser | 3.0L TKS Plus (1G404114 & Up) | 135 | 4-Stroke | 2007-present | 27-8146801 | Throttle body fuel injection |
Technical Specs
- Product Type
- Thermostat Housing Gasket
- Installation
- Between thermostat housing and manifold
- Housing Material
- Gasket material (non-metallic)
- Dimensions
- 9.0 × 11.0 × 1.0 inches
- Weight
- 0.02 lb (9.07 g)
- GTIN
- 745061555105
- Warranty
- No warranty on OEM Mercury parts
What’s in the Box
- 1 x Gasket (27-8146801)
Installation Notes
- Disconnect the vessel's battery and ensure the engine is completely cool.
- Drain the engine coolant to a level below the thermostat housing. Place a catch pan to collect the fluid.
- Loosen and remove the bolts securing the thermostat housing cover.
- Carefully lift the housing and remove the old thermostat and gasket. Note their orientation.
- Thoroughly clean both the housing and manifold mating surfaces. Remove all traces of old gasket material and corrosion.
- Place the new gasket onto the manifold, ensuring alignment with the bolt holes.
- Reinstall the thermostat housing and tighten the bolts to the torque specified in your service manual.
- Refill the cooling system with the appropriate coolant, then reconnect the battery.
- Start the engine and let it reach operating temperature, carefully checking for any leaks around the housing.
Troubleshooting & FAQ
How do I know if this gasket fits my exact MerCruiser 3.0L engine?
The surest way is to match your engine's serial number to the ranges listed in the "Engine & Model Compatibility" table. You can also verify fitment by matching your existing part number to the interchange list: 27-8146801, 27-814680, or 27-33680.
What are the signs of a failed thermostat housing gasket?
Common symptoms include visible coolant leaks around the thermostat housing (often leaving a greenish or pink residue), engine overheating, and an illuminated temperature warning light on your dash. A strong, sweet smell of antifreeze is also a key indicator.
Do I need to use a sealant or adhesive with this gasket?
Generally, this type of gasket is designed to be installed dry. The gasket material is made to compress and seal without additional chemicals. Using sealant can sometimes cause the gasket to slip or fail prematurely. Always consult your engine's official service manual for specific recommendations.
How often should this gasket be replaced?
There is no fixed replacement interval. This gasket should be replaced whenever the thermostat is serviced or replaced, or if you notice any signs of a coolant leak from the housing area.
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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