Sierra 18-4552

Keep your Mercury outboard running cool and reliable with the Sierra 18-4552 water pump repair kit. Designed for boat owners who demand performance without compromise, this rebuild kit restores your engine's cooling system to like-new efficiency. Whether you're prepping for a weekend on the water or tackling routine maintenance, it's the go-to solution for preventing overheating and costly breakdowns.

Why Your Outboard Needs a Reliable Water Pump Rebuild

Outboard motors work hard in harsh marine environments—saltwater, debris, and constant vibration take a toll on water pumps. A worn impeller can spin without gripping, leading to poor water flow, rising engine temps, and potential seizure. The Sierra 18-4552 kit tackles this head-on, delivering OEM-level quality at a fraction of replacement costs. Boat enthusiasts swear by it for its durability and ease of swap during annual servicing.

What's Inside the Sierra 18-4552 Kit

• High-quality neoprene impeller for superior water-pumping action
• Precision-machined wear plate to minimize clearance issues
• Key, O-rings, and gaskets for a leak-free seal
• Stainless steel components to fight corrosion
• All necessary hardware for a complete rebuild

Everything arrives pre-packaged for straightforward assembly, saving you time at the dock or in the garage.

Perfect Fit for Mercury and Mariner Engines

This kit matches specifications for select 4-cylinder Mercury/Mariner outboards in the 90-125 HP range, typically from mid-1970s to early 1980s models. Confirm compatibility with your engine's serial number for the best results—it's engineered to slot right into lower unit housings without modifications. Ideal for DIY mechanics restoring classic powerheads or pros servicing fleets.

Key Benefits of Choosing Sierra Over Stock Parts

Sierra stands out in the aftermarket world for rigorous testing and marine-grade materials. Expect longer impeller life thanks to advanced rubber compounds that resist heat and swelling. Users report cooler running temps and quieter operation post-install. Plus, it's a smart upgrade path—many skip full pump replacements, cutting downtime and expenses while maintaining peak performance.

Spotting Water Pump Failure Early

Don't wait for steam or alarms. Watch for these red flags:

• Weak or erratic tell-tale stream
• Overheating at idle or under load
• Visible impeller chunks in the pee stream
• Unusual lower unit noise

Catch it soon, and a quick rebuild keeps you fishing instead of trailering home early.

Step-by-Step Installation Guide

Rebuilding takes about 1-2 hours with basic tools. Here's a pro tip-filled walkthrough:

1. Drain gear lube and remove lower unit (support the motor).
2. Twist off the old pump housing counterclockwise.
3. Inspect and clean the cam; replace if scored.
4. Lube new impeller with marine grease, install with key aligned.
5. Assemble plate, housing, and seals—torque to spec.
6. Reinstall, refill lube, and test on muffs.

Pro tip: Warm the gearcase slightly to ease impeller removal. Always spin the shaft by hand to check for binding before final assembly.

Maintenance Tips to Extend Pump Life

Maximize your investment:

• Flush with fresh water after saltwater runs.
• Inspect annually or every 100 hours.
• Use Yamalube or Quicksilver gear lube for best lubrication.
• Avoid dry-running the impeller—prime before startup.

These habits turn a seasonal fix into years of trouble-free cooling.

Equip your boat with the Sierra 18-4552 and hit the water confidently. Reliable cooling means more time enjoying the ride, less time wrenching.