Flapper Protector Valve for MerCruiser Alpha One, Bravo Series 12644Q01,12644A1

This is anexhaust flapper valve with a 4-inch inner diameter, designed for marine applications. It serves as a direct replacement for multiple OEM andparts, including Mercury MerCruiser 12644A1 (which supersedes 12644Q01), Sierra 18-4457, and OMC/Johnson/Evinrude 0509495.

Constructed from a EPDM compound with integrated UV stabilizers, this valve is engineered to resist harsh saltwater environments and ozone. Its primary function is to prevent water intrusion into the engine through the exhaust system, protecting it from costly hydrostatic lock. The material is rated for a wide temperature range of -40°F to 221°F.

Key Features:

• Engineered with EPDM rubber for a 3-5x longer service life compared to standard valves.
• Protects engine from water backflow during rough seas or deceleration.
• Includes a marine-grade 316 stainless steel clamp for secure installation.

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM andbrands.

Compatible Engine Models

Confirm your engine model/year. 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.

For Johnson/Evinrude owners, here’s a guide to help you identify your engine’s serial/model: Johnson/Evinrude Serial Number Guide.

This valve offers a universal fit for the following systems:

• MerCruiser Alpha One & Gen II Sterndrives
• MerCruiser Bravo Series Sterndrives
• Any marine exhaust system using a 4.0" outer diameter pipe

Technical Specifications

Package Contents

This is a single-unit sale. The complete kit includes:

• 1x Marine Exhaust Flapper Valve (4")
• 1x Adjustable 316 Stainless Steel Clamp
• Professional Installation Instructions

Installation Guide

Average Installation Time: 15-30 minutes

1. Slide the valve over the 4" exhaust pipe with the flapper facing outward, away from the engine.
2. Position the valve to ensure the flapper can move freely and allow for optimal drainage.
3. Securely tighten the stainless steel clamp to the manufacturer's specified torque.
4. Manually test the flapper to confirm it opens and closes without obstruction.

Maintenance Schedule

• Monthly: Perform a visual inspection for any signs of wear, cracking, or damage.
• Quarterly: Check the tightness of the stainless steel clamp.
• Annually: Conduct a complete inspection and cleaning of the valve.
• 3-5 Years: Replacement is recommended, especially in harsh saltwater environments, to ensure continued protection.

Troubleshooting & FAQ

Q: How do I confirm this fits my engine?
A: This valve provides a universal fit for any 4-inch outer diameter marine exhaust pipe. It is a guaranteed direct replacement for MerCruiser (12644A1, 12644Q01), Sierra (18-4457), and others listed in the cross-reference table. It is ideal for MerCruiser Alpha One, Bravo, and other sterndrives. Always measure your pipe's outer diameter to confirm before purchasing.

Q: How often should I replace it?
A: Our EPDM valve is designed for a service life 3-5 times longer than standard rubber valves. We recommend a visual inspection monthly and a full cleaning annually. For preventative maintenance, especially in harsh saltwater environments, we suggest replacement every 3-5 years.

Q: What are the signs of a failing exhaust flapper?
A: Key signs include water ingestion causing poor engine starts, misfiring, or a gurgling sound from the exhaust at idle. In severe cases, a failed flapper can lead to catastrophic engine damage (hydrostatic lock). Visually inspect your current valve for cracks, brittleness, or missing sections.

Q: OEM vs. Aftermarket?
A: This listing is anreplacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO 9001-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 anreplacement 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.