Exhaust Flapper Protector Valve – Fits MerCruiser (Replaces 12644A1, 12644Q01)

$13.99

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Exhaust Flapper Protector Valve – Fits MerCruiser (Replaces 12644A1, 12644Q01) is backordered and will ship as soon as it is back in stock.

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You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).

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Delivery and Shipping

Free standard shipping on all orders under 1 KG

If you have any questions, feel free to email us at info@sierramarines.com, and we’ll get back to you within 20–36 hours.

Product Details

This 4" Exhaust Flapper Protector Valve is designed for MerCruiser stern drive applications. The rubber flapper prevents water from entering the exhaust system through the outlet while allowing exhaust gases to exit freely. It is made from weather-resistant EPDM rubber with an integrated UV stabilizer to ensure longevity.

This part serves as a direct replacement for MerCruiser parts 12644A1 and 12644Q01. It also provides an interchange for Sierra 18-4457, GLM 89250, and Mallory 9-44001.

Fits externally over any 4" outside-diameter pipe or thru-hull fitting.
Constructed from durable EPDM rubber for a long service life in marine environments.
Includes a marine-grade stainless steel clamp for secure and reliable installation.

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket brands.

Brand	Part Number
MerCruiser	12644A1 / 12644Q01
Sierra	18-4457
GLM	89250
Mallory	9-44001

Engine & Model Compatibility

Confirm your engine model/year in the table below.

Brand	Model	Rated HP	Stroke	OEM Part No.	Notes
MerCruiser	Various Stern Drive Applications	Various	4-Stroke	12644A1/12644Q01	Fits 4" exhaust systems

Technical Specs

Product Type: Exhaust Flapper Protector Valve
Installation: External fitting over 4" OD pipe or thru-hull
Connection: 4" (101.6 mm) internal diameter
Housing Material: EPDM rubber with UV stabilizer
Housing Color: Black
Includes: Stainless steel clamp (4-1/16" to 5")
Warranty: Limited lifetime (Sierra)

What’s in the Box

1 x Exhaust Protector Valve
1 x Stainless Steel Clamp

Installation Notes

Ensure the engine is completely cool before beginning installation.
Locate and access the 4-inch exhaust outlet on your vessel.
Remove the old flapper valve and clamp, if present. Clean any residue from the pipe.
Slide the new exhaust flapper valve over the end of the exhaust pipe until it is seated firmly.
Position the new stainless steel clamp over the collar of the flapper valve.
Tighten the clamp securely with an appropriate tool. Do not overtighten.
Manually check that the flapper moves freely and can create a seal.

Troubleshooting & FAQ

How do I confirm this flapper will fit my engine setup?

This flapper is designed for any system with a 4-inch (101.6 mm) outside diameter exhaust outlet pipe. Verify your pipe's diameter and cross-reference your existing part number with those listed in our Part Number Matrix to ensure compatibility.

What are the signs of a failing exhaust flapper?

Common signs include the rubber flapper being broken, cracked, stiff, or completely missing. A malfunctioning flapper can make a rattling noise at idle and, more critically, may allow water to backflow into the engine, which can cause severe damage.

How often should this part be replaced?

We recommend inspecting the exhaust flappers annually as part of your regular maintenance schedule. Replace them immediately if you see any signs of wear, cracking, or deterioration to prevent water ingestion.

Can I install this part myself?

Yes, this is typically a straightforward installation for those with basic mechanical skills. However, access to the exhaust outlet may be difficult on some boats. When in doubt, professional installation is always recommended.

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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