big-autoparts Marine Impeller Repair Kit for Johnson/Yanmar/Sierra 5/8" 12-Spline — Neoprene Impeller, Gasket & O-Rings

big-autoparts replacement impeller kit is a complete neoprene water pump rebuild set designed to restore cooling flow for outboard and marine engines compatible with Johnson, Yanmar, Sierra and Indmar models.

If your engine's cooling performance has dropped or your water pump shows signs of wear, this kit supplies the essential components to get circulation back to specification without buying a whole pump. The set includes a neoprene impeller, a matching gasket and two O-rings sized for 5/8" shafts and 12-spline drives, meeting OEM cross-reference numbers 09-812B, 119773-42600, 18-3306 and S685007.

How do I know this impeller fits my engine?

Check the manufacturer part numbers and shaft/driven specifications against your current impeller. This kit matches common OEM references used by Johnson, Yanmar, Sierra and Indmar, and the dimensions are provided so you can confirm fit before installation.

• Manufacturer cross-references: 09-812B, 119773-42600, 18-3306, S685007
• Shaft size: 5/8" (16 mm); drive: 12-spline
• Impeller diameter: 2.25" (57.1 mm); width: 1.90" (48.2 mm)
• Material: flexible neoprene for standard marine cooling systems

What components are included and why they matter?

The kit supplies everything needed for a basic impeller service: the impeller itself plus a new gasket and two O-rings to reseal the pump housing. Replacing these wear parts together reduces the risk of leaks and ensures the impeller sits and seals correctly for optimal water flow.

• 1× neoprene impeller sized for the specified shaft and spline
• 1× gasket to restore pump housing seal
• 2× O-rings to replace aging seals and prevent coolant bypass
• All parts pre-tested for dimensional consistency before shipping

How durable is the neoprene construction under normal marine use?

Neoprene is a common choice for marine impellers because it balances flexibility with abrasion and heat resistance for routine engine cooling cycles. Proper installation and periodic inspection will extend service life, while the included seals help protect against premature wear from leaks or misalignment.

• Material: neoprene resilient to oil and coolant exposure
• Designed to flex around vanes for reliable pumping action
• Tested units aim to meet OEM tolerances for fit and function
• Recommended as a routine maintenance replacement item

Is installation difficult for a DIY mechanic?

Basic mechanical skills and common hand tools are usually sufficient to replace the impeller, gasket and O-rings. Follow engine-specific service instructions for pump access, torque settings and priming procedures to ensure proper reassembly and avoid air locks.

• Remove pump cover, extract old impeller carefully to avoid tearing
• Fit new impeller onto the 5/8" shaft, align 12-spline drive as required
• Replace gasket and O-rings, reassemble and test for leaks
• Prime and run engine briefly to verify full water flow

Who is this for: This big-autoparts repair kit is aimed at boat owners, marine mechanics and maintenance technicians who need a reliable, OEM-referenced impeller replacement for select Johnson, Yanmar, Sierra and Indmar applications. It’s ideal for routine cooling-system maintenance or emergency at-dock repairs when restoring proper coolant circulation is the priority.