4" Exhaust Flapper Valve – Fits MerCruiser Stern Drives 1994 & Up (Replaces 12644A1, 12644Q01)
4" Exhaust Flapper Valve – Fits MerCruiser Stern Drives 1994 & Up (Replaces 12644A1, 12644Q01) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
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4" Exhaust Flapper Valve – Fits MerCruiser Stern Drives 1994 &...
4" Exhaust Flapper Valve – Fits MerCruiser Stern Drives 1994 & Up (Replaces 12644A1, 12644Q01) is backordered and will ship as soon as it is back in stock.
Product Details
This 4" Exhaust Flapper Valve – Fits MerCruiser Stern Drives 1994 & Up is designed to prevent water from entering the engine through the exhaust system. Engineered for MerCruiser stern drive models from 1994 and newer with 4-inch exhaust outlets, it is manufactured from a durable, compounded EPDM rubber with a UV stabilizer for weather resistance and long service life.
It serves as a direct replacement for MerCruiser parts 12644A1 and 12644Q01, as well as aftermarket equivalents from Sierra, Mallory, and GLM.
- Installs externally on the exhaust outlet.
- Made from weather-resistant EPDM rubber with a UV stabilizer.
- Kit includes two flapper valves and two stainless steel clamps.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| MerCruiser | 12644A1 |
| MerCruiser | 12644Q01 |
| Mallory | 9-44001 |
| GLM | 89250 |
| Sierra | 18-4457 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This component is designed primarily for MerCruiser stern drives using a 4-inch exhaust system.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| MerCruiser | Various Stern Drive Models | Various | 4-Stroke | 1994 & Up | 12644A1, 12644Q01 | Fits 4" exhaust systems |
Technical Specs
- Product Type
- Exhaust Flapper Valve
- Installation
- External, with clamp
- Size
- 4" (101.6 mm)
- Material
- EPDM Rubber with UV stabilizer
- Connection
- Stainless Steel Clamp (4-1/16" to 5")
- Housing Material
- Rubber construction
- Housing Color
- Black
- Dimensions
- 7.25 × 6.75 × 2 in (184.15 × 171.45 × 50.8 mm)
- Weight
- 0.5 lbs (0.227 kg)
- Warranty
- Limited lifetime (Sierra brand)
What’s in the Box
- 2 x Exhaust Protector Valve (12644A1, 12644Q01)
- 2 x Stainless Steel Clamp (4-1/16" to 5")
Installation Notes
- Ensure the engine is off, cool, and the vessel is stable.
- Locate the exhaust outlets on the transom.
- Loosen and remove the old clamp securing the existing flapper valve.
- Remove the old flapper and clean the mounting surface on the exhaust pipe thoroughly.
- Position the new flapper valve over the exhaust outlet, ensuring it is correctly oriented to open outwards.
- Slide the new stainless steel clamp over the flapper and position it in the designated groove.
- Tighten the clamp securely with a screwdriver or nut driver until snug. Do not overtighten.
- Repeat the process for the second exhaust outlet if applicable.
Troubleshooting & FAQ
How do I know if this flapper valve will fit my specific MerCruiser engine?
This valve is designed for MerCruiser stern drive models from 1994 and newer that use a 4" (101.6 mm) outside diameter exhaust system. The most reliable method is to match the OEM part number (12644A1 or 12644Q01) from your service manual or by inspecting the existing part.
What are the signs of a failing exhaust flapper?
Signs of a bad or missing flapper include visible cracks, stiffness, or brittleness in the rubber; a rattling noise from the exhaust at idle; or, in severe cases, water ingestion leading to engine hydrolock. Regular inspection during seasonal maintenance is recommended.
How often should I replace my exhaust flappers?
It is best practice to inspect them annually. Replacement frequency depends on usage and environmental factors (saltwater vs. freshwater). Replace them immediately if you see any signs of wear, cracking, or if the rubber has lost its flexibility.
Can I install these myself?
Yes, this is a common DIY task for boat owners with basic mechanical skills. The process involves removing the old clamp and flapper and securing the new one. However, if you are unsure, professional installation is always recommended to prevent improper installation that could lead to engine damage.
Is this a single flapper or a pair?
This product is sold as a kit that includes two flapper valves and two corresponding stainless steel clamps, suitable for a twin-exhaust setup.
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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