Impeller for Yamaha/Mariner 40 HP (1990–1997) – Reliable Cooling Impeller

Specially crafted for the classic Yamaha/Mariner 40 HP outboard, this impeller restores factory cooling performance in older models (early 1990s). If you own a boat with such a motor, you likely know how important it is to keep the cooling system in good shape, as older engines are less forgiving of overheating. This impeller 52.352.00 (CEF code 500352) is a direct replacement for the original Yamaha part #6F5-44352-00 used in 40 HP motors manufactured roughly between 1990 and 1997.

• Compatibility: It’s intended for Yamaha 40 HP 2-stroke outboards from the 1990s, including models like the Yamaha 40V/40X (40 HP) produced around 1990–1997. Many of these engines had Mariner-branded equivalents (due to the Brunswick-Yamaha cooperation in that era), so if you have a Mariner 40HP of the same years, this impeller will fit as well. For confirmation, check if your old impeller has the marking 6F5-44352-00 – that’s a sure sign of compatibility.
• Use Cases: Yamaha 40 HP engines of this period were often mounted on 4–5 meter boats – typically small fishing vessels, utility jon boats, or runabouts for leisure. These engines are usually twin-cylinder with a simple design, but effective cooling relies on a healthy impeller. Over the years, the impeller material can harden or blades wear down, reducing water flow. Replacing it with a new impeller brings back the pump’s full capacity – crucial in hot weather or at high RPM when the engine is under greater thermal load.
• Performance: The impeller features 6 blades that provide smooth, consistent flow. The outer diameter (~46 mm, approximate) and height (~19 mm) are precisely engineered for the water pump housing of these 40HP motors, and the inner spline hub (~15.8 mm) fits snugly onto the driveshaft key. This means that with proper installation, you’ll get optimal sealing and pressure – water will circulate through the engine’s cooling passages as intended, carrying away excess heat. The result is stable engine temperatures and reliable performance.
• Quality: CEF uses a high-quality rubber polymer that withstands temperature fluctuations and the continuous friction inside the water pump. The impeller is saltwater resistant, which is important if you operate in marine environments – the material won’t break down quickly due to salt exposure. It’s also designed to endure prolonged storage without cracking, a plus for seasonal boats that sit idle in the off-season. With proper use, this impeller will give several seasons of dependable service. It’s essentially bringing your engine back closer to its original cooling specs.
• Maintenance: For older engines like the 40HP Yamaha, it’s good practice to inspect the impeller annually. If your boat is used in a commercial setting (e.g., guiding or daily use), yearly replacement is recommended. For recreational use, you might stretch it to every other year, but always watch the tell-tale water stream – if it weakens or sputters, that’s a warning sign. When replacing the impeller, also check the condition of the metal cup, the drive key, and the pump gaskets – if they’re worn, renewing them along with the impeller will restore the system to like-new condition. Taking these steps ensures your trusty 40HP outboard remains cool and runs smoothly, avoiding unexpected downtime on the water.