Sierra 18-3178 Marine Water Pump Wear Plate for Johnson/Evinrude OMC Outboard

The Sierra 18-3178 is a precision-replacement water pump wear plate designed for Johnson and Evinrude OMC outboard motors. This wear plate sits beneath the water pump impeller and provides the critical mating surface necessary for efficient water flow through the engine's cooling system. Replacing a worn or damaged wear plate helps restore proper impeller function and prevents engine overheating.

Key Features:

• Marine-grade, non-corrosive construction for long-lasting durability in saltwater and freshwater environments
• Meets or exceeds original equipment (OEM) quality standards
• Direct-fit replacement — no modification required
• Commonly used as part of a complete water pump service or rebuild

Cross-Reference Part Numbers:

• OEM OMC/Johnson/Evinrude: 318995
• GLM: 12610
• Mallory: 9-43404
• Sierra: 18-3178

This wear plate is a standard component in Sierra's water pump repair and impeller kits for 9.9 HP and 15 HP Johnson/Evinrude outboards (2-stroke 1974 and up; 4-stroke 1995 and up). It is sold as an individual replacement part, allowing for targeted servicing without purchasing a full kit.