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)

This 4" exhaust flapper valve is designed for MerCruiser stern drive exhaust systems from 1994 and newer. It features a compounded EPDM rubber construction with a UV stabilizer to prevent water from entering the engine through the exhaust system, ensuring long-lasting performance in marine environments.

This part directly replaces MerCruiser 12644A1 and 12644Q01, Mallory 9-44001, GLM 89250, and Sierra 18-4457.

• Material: Compounded, weather-resistant EPDM rubber with UV stabilizer.
• Installation: External mount on 4" exhaust systems with the included clamp.
• Complete Kit: Includes two exhaust flapper valves and two stainless steel clamps.

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below. For Mercury owners, here’s a guide to help you identify your engine’s serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

Technical Specifications

Package Contents

• 2 x Exhaust Protector Valve (Replaces 12644A1, 12644Q01)
• 2 x Stainless Steel Clamp (4-1/16" to 5")

Installation Guide

1. Safety First: Ensure the engine is completely cool and turned off before beginning work.
2. Locate Old Flapper: Identify the existing external exhaust flapper valve on the exhaust pipe near the transom.
3. Remove Clamp: Loosen and remove the clamp that secures the old flapper valve.
4. Remove Old Flapper: Slide the old, worn flapper off the pipe. Thoroughly clean any dirt or residue from the pipe surface.
5. Position New Flapper: Slide the new flapper valve onto the pipe. Ensure it is oriented correctly to let exhaust out and prevent water from getting in.
6. Secure New Flapper: Use the provided stainless steel clamp to secure the new valve. Tighten it firmly but do not overtighten, which could damage the rubber.
7. Check Operation: Manually check that the flapper moves freely and can form a seal when closed.
8. Final Test: Briefly start the engine to check for any exhaust leaks around the new connection.

Troubleshooting & FAQ

Q: How do I know if this flapper valve will fit my engine?

A: This 4" flapper valve is designed for MerCruiser stern drive models from 1994 and newer and also fits some OMC/Volvo applications with 4" exhaust systems. The most reliable way to confirm fitment is to measure your exhaust pipe's outer diameter and cross-reference your existing part number with those listed (e.g., 12644A1, 9-44001).

Q: What are the signs that my exhaust flapper needs replacement?

A: Common signs of a failing exhaust flapper include a persistent rattling or clanking sound from the stern at idle, visible cracks or damage to the rubber, or finding pieces of the old flapper in the exhaust. A damaged flapper can allow water to enter the engine, leading to serious damage.

Q: Is this an internal or external flapper?

A: This is an external flapper valve that is installed on the outside of the exhaust Y-pipe and secured with a clamp.

Q: OEM vs. Aftermarket?

A: This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

Q: How fast do you ship and how much does it cost?

A: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

Q: What is your warranty and return policy?

A: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.