Sierra 18-3147
Sierra 18-3147 — Product description
Upgrade Your Boat's Cooling System with the Sierra 18-3147 Water Pump Kit
Keeping your marine engine cool under pressure is non-negotiable, especially during long days on the water. The Sierra 18-3147 water pump kit steps in as a dependable aftermarket solution, designed to match the performance of original equipment while delivering lasting reliability. This kit directly replaces the Mercury 817275Q series pumps, ensuring seamless integration into your existing setup without the hassle of custom modifications.
Perfect Fit for Popular Mercruiser Engines
Crafted for precision, the Sierra 18-3147 fits a wide range of Mercruiser stern drive and inboard models, particularly those with GM V8 blocks from the 1980s through the early 2000s. Think Alpha One, Bravo One, and similar configurations running 4.3L, 5.0L, 5.7L, and 7.4L engines. Boat owners rave about its drop-in compatibility, saving hours of trial-and-error during replacement. Whether you're maintaining a classic cruiser or prepping a tournament bass boat, this kit restores optimal coolant flow to prevent overheating and engine damage.
What's Inside the Kit: Complete Rebuild Ready
- High-flow impeller for maximum cooling efficiency
- Durable housing constructed from corrosion-resistant materials to battle saltwater exposure
- Wear plate for extended service life
- Gaskets, O-rings, and seals for a leak-proof install
- Key-driven design for positive impeller engagement, reducing slip under high RPMs
Every component undergoes rigorous testing to meet or exceed OEM standards, so you get factory-level performance at a fraction of the cost. No more piecemeal parts hunting—this all-in-one kit has you back in the water fast.
Why Sierra 18-3147 Outshines the Competition
Sierra's engineering focuses on real-world boating demands: relentless sun, salty spray, and high-speed runs. Unlike generic imports that warp or seize prematurely, this pump features a robust bronze impeller and stainless steel fasteners that shrug off galvanic corrosion. Users report 20-30% better flow rates compared to worn stock units, translating to cooler engine temps and smoother operation. It's not just a replacement; it's an upgrade that extends your engine's lifespan and boosts resale value.
Effortless Installation Tips for DIY Boaters
Swapping out your old pump? You'll need basic tools: socket set, gasket scraper, and marine sealant. Drain the coolant, remove the lower unit or raw water housing, and inspect for debris in the pickup tube. Align the impeller key precisely, torque to spec (usually 75-100 ft-lbs on the pulley), and bleed the system before firing up. Pro tip: While you're in there, check the thermostat and hoses for wear—preventive maintenance pays dividends. Most installs wrap up in under two hours, even for weekend warriors.
Long-Term Maintenance for Peak Performance
To maximize longevity, flush your cooling system with fresh water after every saltwater trip. Inspect the impeller annually or every 100 hours of use—look for glazing, chunks missing, or swelling from age. Pair this pump with a quality zinc anode and anti-freeze for winter storage. Boaters who follow these steps often see 3-5 years of trouble-free service, far outpacing neglected OEM parts.
Frequently Asked Questions
Is the Sierra 18-3147 compatible with my Mercruiser 5.7L engine?
Yes, it fits most Mercruiser 5.7L V8 models from 1983-1995, including Alpha and Bravo drives. Confirm your serial number range for exact match, but it's a direct swap for 817275Q pumps.
How do I know when to replace my boat's water pump?
Watch for signs like steam from the exhaust, rising engine temps, or reduced pee stream from the tell-tale. Annual impeller checks catch issues early.
Does this kit include the pulley?
The core pump kit focuses on the impeller housing and internals. Reuse your existing pulley unless it's damaged—Sierra offers it separately if needed.
Can I use this in freshwater only boats?
Absolutely. Its corrosion-resistant build works great in lakes and rivers, though freshwater extends impeller life even further.
What's the difference between rubber and neoprene impellers in this kit?
Sierra uses neoprene for superior heat and oil resistance, ideal for mixed gas scenarios. It outperforms basic rubber in demanding marine environments.
Will this pump work with closed cooling systems?
It's designed for raw water cooling but pairs perfectly with heat exchangers in closed-loop setups. Ensure your exchanger is functioning for best results.
How does Sierra quality compare to OEM Mercury parts?
Sierra meets ABYC and NMMA standards, with many boaters finding it indistinguishable from Mercury in fit and flow. It's a trusted choice for rebuilds.
SKU: NVN-4003606
MPN: 18-3147
UPC: 808282112844
Technical specifications
| Brand | Sierra Engine Parts |
| Model | Sierra 18-3147 |
| SKU / MFR# | 4003606 |
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