Sierra 18-3431 6L2-W0078-00-00 Yamaha Wp Kit

Keep your Yamaha outboard running cool and reliable with this high-quality water pump kit. Designed as a direct replacement for the original equipment, it ensures optimal coolant flow to prevent overheating during those long days on the water. Whether you're tackling offshore adventures or leisurely cruises, a fresh water pump rebuild restores peak performance and extends engine life.

Essential Role in Your Outboard's Cooling System

The water pump is the heart of your Yamaha's cooling system, circulating seawater through the engine block and exhaust to dissipate heat. Over time, impeller blades wear, housings corrode, and seals fail from constant exposure to saltwater and debris. Neglecting it leads to rising temperatures, reduced power, and potential catastrophic damage. This kit delivers everything needed for a complete overhaul, bringing back factory-level efficiency without the hassle of sourcing individual parts.

Precision Components for Reliable Operation

• Durable Impeller: Precision-molded rubber with flexible vanes that maintain shape under high RPMs, ensuring consistent water intake even in shallow or debris-filled waters.
• Corrosion-Resistant Housing: Engineered with marine-grade materials to withstand electrolysis and galvanic corrosion common in saltwater environments.
• High-Quality Gaskets and Seals: OEM-spec designs that create airtight seals, preventing leaks and air pockets that disrupt flow.
• Stainless Steel Wear Plate: Protects against abrasion, extending the life of the pump assembly.

Every piece undergoes rigorous testing to meet or exceed original specifications, giving you peace of mind on the water.

Broad Compatibility Across Yamaha Models

This kit fits a range of Yamaha 2-stroke outboards from the late '80s through the '90s, including popular 40HP and 50HP powerheads. It's a plug-and-play solution for engines where the original pump shows signs of wear like diminished stream from the tell-tale, unusual engine noise, or steam from the exhaust. Always cross-reference with your service manual to confirm fitment for your specific serial number range.

Step-by-Step Installation Guide

Reviving your water pump is a straightforward DIY job that saves time and money. Here's a proven approach:

1. Preparation: Tilt the engine up, remove the lower unit bolts, and slide off the gearcase. Drain any residual gear lube and flush the cooling passages.
2. Disassembly: Pry out the old impeller with needle-nose pliers, noting its orientation. Clean the housing thoroughly, removing scale and old gasket material.
3. Assembly: Lubricate the new impeller with marine grease, install it with vanes trailing in the direction of rotation (typically marked). Position the keyway correctly and torque the retainer to spec.
4. Reinstallation: Replace gaskets, align the driveshaft spline, and secure the lower unit. Prime the system by running in a barrel of water before sea trial.
5. Testing: Monitor the tell-tale stream—it should be strong and steady at idle and wide-open throttle.

Pro tip: Replace the pump every 2-3 years or 300 hours in saltwater use to stay ahead of failures.

Why Boaters Trust This Aftermarket Upgrade

Unlike stock parts that wear quickly, this kit uses upgraded materials for better longevity and quieter operation. Boaters report cooler running temps, smoother idling, and no more mid-trip breakdowns. It's an investment that pays off in fewer repairs and more time fishing or exploring. Pair it with fresh gear lube and anode inspections for comprehensive lower unit care.

Frequently Asked Questions