Impeller for Yamaha 300/350 HP – Heavy-Duty Water Pump Impeller for Large Outboards

This heavy-duty impeller is specifically engineered for Yamaha’s most powerful outboard motors: 300 HP and 350 HP models. As a direct replacement for Yamaha OEM part 6AW-44352-00, it delivers the high water flow needed to keep large engines cool under extreme conditions. Manufactured by CEF, it meets or exceeds the original specifications, making it a trustworthy choice when servicing your engine’s cooling system.

• Compatibility: Designed for Yamaha 4-stroke outboards, including the F300 (300 HP) V6 and F350 (350 HP) V8 models. It is also compatible with equivalent Yamaha MARX series models (if applicable) and certain Mercury/Mariner engines in this horsepower range (for example, Mercury Verado 300) that use the same style impeller.
• Use Cases: Ideal for large offshore boats and high-performance powerboats (typically 7–10+ meters in length) equipped with engines of 300 HP and above. This impeller ensures your engine’s cooling system can cope with demanding conditions – whether you’re on extended high-speed runs, towing water sport enthusiasts, or operating in hot tropical climates.
• Performance: The heavy-duty 6-blade design with a large inner hub diameter (Ø A ≈ 24.6 mm) and outer diameter (Ø B ≈ 89 mm) provides an exceptionally high volume of water flow through the engine. This high coolant flow keeps engine temperatures stable even during prolonged full-throttle operation. It protects critical engine components – such as cylinder heads and exhaust manifolds – from overheating due to the added cooling capacity.
• Durability: The impeller is made from nitrile rubber (NBR), which offers superior resistance to elevated temperatures and potential fuel or oil contaminants in the water. This makes it especially suitable for high-horsepower engines and even some inboard cooling systems. The material resists abrasive wear from particles in the water, extending the impeller’s lifespan even in harsh conditions (for example, silty or sandy waters). The robust construction means it can withstand the greater rotational forces and prolonged use associated with big outboards.
• Maintenance: For engines of this class, manufacturers recommend inspecting the water pump annually. Replacing the impeller at least once per year or roughly every 100 operating hours is prudent to ensure engine reliability. If operating in extreme conditions (such as frequent high-speed runs or very warm waters), more frequent checks might be necessary. Always monitor your engine’s operating temperature – any unusual rise could indicate a worn impeller that needs immediate replacement.
• Professional Installation: While impeller replacement is a routine maintenance task, with these large engines, careful installation is key. Ensure the pump’s key (drive pin) and gaskets are properly positioned along with the new impeller. Proper installation guarantees optimal pump performance and maximizes the service life of the impeller. Following the engine’s service manual or having a professional marine technician perform the installation can be beneficial for such critical components.