Sierra 18-3012 Marine Neoprene Water Pump Impeller 6-Fin for Mercury/Mariner Outboard

The Sierra 18-3012 is a neoprene water pump impeller designed as a direct replacement for Mercury and Mariner outboard motors. Built to meet or exceed original equipment specifications, this impeller features 6 flexible neoprene vanes molded around a brass hub, delivering reliable cooling water flow to protect your engine from overheating.

The impeller's flexible vanes rotate on an eccentric within the water pump housing, drawing and pushing coolant water through the engine's cooling circuit. A failed or worn impeller will reduce or stop water flow entirely, risking serious engine damage — making timely replacement a critical part of routine outboard maintenance.

Key Features:

• Neoprene construction with 6 flexible vanes for dependable water flow
• Brass hub for durability and corrosion resistance
• Meets or exceeds OEM performance specifications
• Direct replacement for Mercury OEM part number 47-22748
• Cross-references: Mallory 9-45308, GLM 89600, Mercury Marine 47-22748
• One impeller included per package

Specifications:

• Overall Diameter: 31.61 mm (1.24 in)
• Height: 14.20 mm (0.56 in)
• Shaft Diameter: 11.60 mm (0.46 in)
• Number of Fins/Blades: 6
• Material: Neoprene with brass hub

Installation Tip: Lubricate the impeller with silicone grease, glycerine, or dish soap before installation. When seating the impeller, turn the driveshaft clockwise while pressing down to allow the vanes to fold correctly into the pump housing.

Sierra recommends inspecting or replacing your water pump impeller annually as part of standard outboard service. Keeping a spare impeller onboard is always a smart practice when operating in open water.