6S5-12121-00-00 Exhaust Valve for Yamaha 255 FSH Sport H 1800 2024-2026

Exhaust Valve for Yamaha

This exhaust valve (OEM cross-reference 6S5-12121-00-00) controls exhaust flow at the cylinder head, sealing combustion gases on the compression and power strokes and opening to release them, keeping your Yamaha marine engine running cleanly and efficiently.

Overview

This exhaust valve is a direct replacement component built to OEM cross-reference 6S5-12121-00-00 for the Yamaha 1800 engine used in 255 FSH Sport H models from 2024 to 2026. It manages the release of burned gases from the combustion chamber, helping preserve compression, power output, and smooth operation on the water. It suits owners performing a top-end rebuild or replacing a burned or sticking valve.

Built For Performance

• Manufactured to OEM cross-reference 6S5-12121-00-00 for a precise fit
• Heat-resistant alloy construction suited to sustained marine engine temperatures
• Precision-machined stem and head for consistent sealing at the valve seat
• Built to handle the high-rpm duty cycles of the Yamaha 1800 marine engine
• Direct-fit replacement requiring no modification to the cylinder head

Fits These Machines

• for Yamaha 255 FSH Sport H 1800 (2024-2026)

On-The-Job Use

• Top-end rebuilds and valve jobs on Yamaha 1800 marine engines
• Replacing a burned, cracked, or poorly sealing exhaust valve
• Restoring compression and exhaust flow after extended saltwater use
• Routine maintenance on 255 FSH Sport H boats

Specs At A Glance

Good To Know

Q: Should exhaust valves be replaced as a set? A: Replacing all valves in the cylinder head at once is common practice during a rebuild, since wear tends to be shared across the set. Confirm your engine's service requirements before ordering individual pieces.

Q: How do I know if my exhaust valve needs replacing? A: Symptoms include loss of compression, rough running, or visible burning and pitting on the valve face. A leak-down or compression test can confirm the diagnosis.

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