Thermostat Gasket – Fits Yamaha 48-55HP (663-12414-A0-00, 663-12414-00-00)
Thermostat Gasket – Fits Yamaha 48-55HP (663-12414-A0-00, 663-12414-00-00) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
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Thermostat Gasket – Fits Yamaha 48-55HP (663-12414-A0-00, 663-12414...
Product Details
This Thermostat Gasket – Fits Yamaha 48-55HP (663-12414-A0-00, 663-12414-00-00) provides a reliable seal for the thermostat housing on Yamaha 2-Stroke 48-55HP outboard engines (1989–2000), including C55, E48, and CV55 series models.
It serves as a direct interchange for Yamaha part numbers 663-12414-00-00 and 663-12414-A0-00, as well as GLM Marine 38066.
- Ensures a precise, leak-free fit for the thermostat housing.
- Direct replacement for a straightforward installation.
- Engineered to match original equipment specifications for performance and durability.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Notes |
|---|---|---|
| Yamaha | 663-12414-00-00 | Superseded by 663-12414-A0-00 |
| Yamaha | 663-12414-A0-00 | Current OEM part number |
| GLM Marine | 38066 | Aftermarket equivalent |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This gasket is designed for specific Yamaha outboard models. Please verify your exact model number for a correct fit.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. |
|---|---|---|---|---|---|
| Yamaha | CV55ELF | 55 | 2-Stroke | 1989 | 663-12414-00-00/663-12414-A0-00 |
| Yamaha | CV55ELD | 55 | 2-Stroke | 1990 | 663-12414-00-00/663-12414-A0-00 |
| Yamaha | C55ELRP | 55 | 2-Stroke | 1991 | 663-12414-00-00/663-12414-A0-00 |
| Yamaha | C55ELRQ | 55 | 2-Stroke | 1992 | 663-12414-00-00/663-12414-A0-00 |
| Yamaha | C55ELRR, C55TLRR | 55 | 2-Stroke | 1993 | 663-12414-00-00/663-12414-A0-00 |
| Yamaha | C55ELRS, C55TLRS | 55 | 2-Stroke | 1994 | 663-12414-00-00/663-12414-A0-00 |
| Yamaha | C55ELRT, C55ERT, C55TLRT, C55TRT | 55 | 2-Stroke | 1995 | 663-12414-00-00/663-12414-A0-00 |
| Yamaha | E48MLHT | 48 | 2-Stroke | 1995 | 663-12414-00-00/663-12414-A0-00 |
| Yamaha | E48MLHU | 48 | 2-Stroke | 1996 | 663-12414-00-00/663-12414-A0-00 |
| Yamaha | E48MLHV | 48 | 2-Stroke | 1997 | 663-12414-00-00/663-12414-A0-00 |
| Yamaha | E48MLHW | 48 | 2-Stroke | 1998 | 663-12414-00-00/663-12414-A0-00 |
| Yamaha | E48MLHX | 48 | 2-Stroke | 1999 | 663-12414-00-00/663-12414-A0-00 |
| Yamaha | E48MLHY | 48 | 2-Stroke | 2000 | 663-12414-00-00/663-12414-A0-00 |
Technical Specs
- Product Type
- Thermostat Cover Gasket
- Installation
- Direct replacement
- Dimensions
- 8.5 × 6.0 × 0.1 in (215.9 × 152.4 × 2.54 mm)
- Weight
- 0.04 lb (0.018 kg)
- Other Technical Attributes
- Superseded by part number 663-12414-A0-00
What’s in the Box
- 1 x Gasket, Cover (663-12414-A0-00)
Installation Notes
- Ensure the engine is off and cool. Disconnect the battery and place a container beneath the engine to catch any drained coolant.
- Locate the thermostat housing and carefully remove the bolts holding the cover in place.
- Gently remove the cover and the old gasket. Be prepared for some residual coolant to spill out.
- Thoroughly clean both the housing and cover mating surfaces. Remove all traces of the old gasket and any sealant residue to ensure a proper seal.
- Position the new gasket correctly on the housing, aligning it with the bolt holes.
- Reattach the cover and tighten the bolts in a crisscross pattern to the manufacturer's specified torque to ensure even pressure.
- Refill the cooling system with the appropriate coolant.
- Reconnect the battery, start the engine, and carefully inspect the housing for any signs of leaks as the engine warms up.
Troubleshooting & FAQ
How do I know if this gasket fits my Yamaha engine?
This gasket is designed for Yamaha 2-Stroke 48-55HP outboards made between 1989 and 2000. To be certain, please check your engine model and year against the comprehensive list in the "Engine & Model Compatibility" section above.
What are the signs of a failing thermostat gasket?
Common signs include visible coolant leaks around the thermostat housing, an engine that is overheating, or a fluctuating temperature gauge. You may also notice white steam or a sweet smell from the engine area.
Do I need to use sealant with this gasket?
This gasket is designed to seal without additional sealant. However, always consult your engine's service manual for the manufacturer's specific recommendations. In some cases, a very thin layer of non-hardening sealant may be advised on older or pitted surfaces.
What is the difference between part 663-12414-00-00 and 663-12414-A0-00?
The part number 663-12414-A0-00 has superseded 663-12414-00-00. This is a standard update from Yamaha, and the newer part is the direct, correct replacement for the older one. Our gasket replaces both versions.
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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