Exhaust 4” Protector Flapper for MerCruiser Mercury Sterndrive 12644A1, 18-4457

Exhaust 4” Protector Flapper for MerCruiser and Mercury

This exhaust protector flapper replaces OEM part numbers 12644A1 and 18-4457 for MerCruiser and Mercury sterndrive systems.

Overview

This 4-inch exhaust protector flapper is a direct replacement for MerCruiser and Mercury sterndrive exhaust systems. It prevents backflow and debris entry while maintaining proper exhaust flow. Designed to fit 4-inch exhaust outlets, it is a common maintenance item for boat owners.

Built For Performance

• Stainless steel hinge pin resists corrosion
• Flexible rubber flap seals tightly against outlet
• Pre-assembled for quick installation
• Compatible with MerCruiser and Mercury aftermarket exhaust systems
• Lightweight design reduces stress on mounting points

On-The-Job Use

• Prevents water and debris from entering exhaust when not in use
• Used on sterndrive boats with through-hull exhaust outlets
• Replaces worn or missing flapper protectors during routine maintenance
• Works in both fresh and saltwater conditions

Specs At A Glance

Good To Know

Q: Does this flapper fit all MerCruiser sterndrives? A: It fits many MerCruiser and Mercury sterndrive models with a 4-inch exhaust outlet. Check your existing part number against 12644A1 or 18-4457.

Q: Can I install this myself? A: Yes, installation typically requires removing two screws and replacing the old flapper. Ensure the exhaust outlet is clean before mounting.

Slight variation in finish or dimensions may occur between production runs, and fit can depend on serial number, so confirm compatibility before ordering.