Mercury/Mariner 65–225 HP Impeller (2-Stroke & Optimax, Alpha One Gen I)

This impeller ensures proper cooling for a broad range of Mercury/Mariner two-stroke outboards and early Optimax direct-injection engines, covering mid-range and V6 powerplants from approximately 65 HP up to 225 HP (late 1970s through late 1990s models). It also serves as the correct impeller for MerCruiser Alpha One Gen I sterndrives (pre-1992), which utilize a similar water pump in the drive unit. By installing this impeller, owners can maintain OEM-level cooling performance in older engines and drive systems that might otherwise be prone to overheating due to a worn impeller.

Engineered with a 6-vane design, this impeller provides ample water flow through the cooling system at both idle and high speeds. It's built from marine-grade rubber to resist wear and swelling, ensuring a secure fit inside the pump housing. This impeller is a dependable replacement that helps extend the service life of classic Mercury motors and vintage MerCruiser drives by safeguarding them from overheating damage.

• Classic Mercury Coverage: Great for older Mercury outboards such as classic 3-cylinder 70/90 HP models, 4-cylinder “Classic Fifty” 45 HP, and V6 engines (135/150/175/200/225 HP) from the 1980s and 90s. Restores cooling efficiency in XRi, EFI, and early Optimax versions of these engines.
• MerCruiser Alpha I: Essential for maintaining MerCruiser Alpha One Gen I sterndrive cooling (found on many pre-’92 MerCruiser-powered boats). This impeller keeps inboard/outboard setups running at proper temperature, protecting engine and drive components.
• Use Case: Suited for boats ~5–7 m (17–23 ft) with mid-to-large outboards or small-block V6 sterndrives of that era – including ski boats, bass boats, and cruiser boats. Provides reliable cooling during water sports or cruising, even on hot summer days.
• Durable Build: Made of tough neoprene rubber formulated for marine environments. Each impeller comes with the required key to lock onto the driveshaft, ensuring a positive drive and consistent pump performance.
• Service Interval: It’s recommended to inspect and replace this impeller at least every 1–2 boating seasons on older engines. Regular replacement prevents unexpected overheating issues in aging cooling systems, especially when operating in debris-prone waters.