Sierra 18-3246 Impeller

Keeping your outboard motor cool under pressure is non-negotiable on the water. A worn or damaged impeller can lead to overheating, reduced performance, and costly engine repairs. The Sierra 18-3246 impeller steps in as a dependable upgrade, crafted to restore optimal water flow in your marine engine's pump system. Boat owners swear by its durability during long hauls and choppy conditions, ensuring your engine stays protected season after season.

Superior Design for Peak Performance

Engineered with precision, this impeller features flexible neoprene vanes that conform perfectly to the pump housing, maximizing water intake even at high RPMs. Unlike brittle alternatives, it resists cracking from heat cycles or debris ingestion, delivering consistent cooling for inline and V-drive setups. Its exact OEM-spec dimensions guarantee a seamless fit, eliminating vibrations and leaks that plague inferior parts.

• High-Quality Neoprene Construction: Withstands temperatures up to 250°F and resists swelling in ethanol-blended fuels.
• Precision Blades: 12 vanes optimized for efficient priming and flow rates up to 40 GPM.
• Corrosion-Resistant: Ideal for saltwater environments, preventing premature wear.
• Balanced Rotation: Reduces wear on the pump shaft and extends overall service life.

Seamless Compatibility with Popular Outboards

This impeller slots right into a range of 2-stroke and 4-stroke engines from leading brands. It's a direct replacement for models in the 4-9.9 HP class, commonly found on dinghies, fishing boats, and pontoons. Verify your engine's serial number against service manuals, but it's proven reliable in applications like early Mercury, Johnson, and Evinrude powerheads. Pro tip: Pair it with a fresh wear plate for even better longevity.

Step-by-Step Installation Guide

Swapping out your old impeller takes under an hour with basic tools—no special skills required. Here's how to do it right:

1. Prep Work: Tilt the motor up, remove the lower unit, and drain any water. Wear gloves to handle the old impeller safely.
2. Disassemble: Twist off the pump cover (usually 4-6 screws), inspect the housing for scoring, and gently pry out the worn impeller using pliers or a puller tool.
3. Lube and Insert: Apply marine grease to the new Sierra 18-3246 impeller and shaft. Align the keyway, then press it on by hand or with a socket—never hammer it.
4. Reassemble: Torque the cover screws to spec (typically 60-84 in-lbs), reinstall the lower unit, and test-prime with muffs before launch.
5. Final Check: Run the motor on a hose; solid water flow from the tell-tale confirms success.

Common pitfall: Install with the vanes folding rearward for proper rotation. If it feels stiff, soak in hot water for 10 minutes to soften.

Pro Maintenance Tips to Avoid Breakdowns

Inspect your impeller annually or every 100 hours—whichever comes first. Signs of trouble include weak pee stream, milky exhaust, or surging temps. Flush with fresh water after every saltwater trip, and store the motor dry. For heavy users, upgrade to a rebuild kit with a stainless steel drive key to prevent shearing. This simple routine can double your impeller's lifespan, saving you downtime on prime fishing days.

Frequently Asked Questions

Equip your boat with the Sierra 18-3246 and hit the water confidently—reliable cooling means more time fishing, cruising, and enjoying the ride.