Sierra Marine Water Pump Kit 18-3150 – Yamaha 20-25HP 2-Stroke Cooling System Rebuild
Free returns on all eligible orders
You have 30 days to request a return. All sale items are final sale.
The Sierra 18-3150 Water Pump Kit is a complete internal rebuild kit designed for Yamaha 2-stroke 20HP and 25HP outboards. This kit restores proper cooling system performance by replacing all critical wear components inside the water pump assembly.
This is a “without housing” kit, meaning it includes the impeller, wear plate, cup, seals, and gaskets while reusing the existing pump housing. Ideal for routine maintenance or resolving weak water flow, overheating, or impeller failure.
Built to meet or exceed OEM specifications, Sierra components ensure reliable cooling performance and long service life in marine environments.
Key Features
- Complete internal water pump rebuild kit (housing not included)
- Includes impeller, wear plate, cup, gaskets, seals, and hardware
- Restores proper cooling water flow and engine temperature control
- Direct OEM replacement fit and performance
- Designed for Yamaha 2-stroke mid-range outboards
- Sierra limited lifetime warranty
Engine Compatibility
Yamaha Outboards (2-Stroke)
- 20 HP
- 25 HP
➡️ Fits 2-cylinder Yamaha 2-stroke engines with standard lower units.
Mariner (Yamaha-built models)
- 20 HP
- 25 HP
➡️ Cross-compatible with Yamaha-manufactured Mariner engines using the same platform.
Serial Number Fitment Notice
Fitment varies by model year and lower unit configuration.
⚠️ Always confirm compatibility using your engine serial number, especially for:
- Early vs late production models
- Yamaha vs Yamaha-built Mariner variations
When This Part Needs Replacement
Replace the water pump kit if you notice:
- Weak or no telltale stream
- Engine overheating
- Reduced cooling at idle
- Impeller cracking, swelling, or hardening
- Engine sitting unused for extended periods
Recommended service interval: every 100 hours or annually
Installation Notes
- Housing is not included — inspect and replace if worn
- Install impeller in correct rotation direction
- Apply marine grease during installation
- Replace seals and key components to prevent failure
- Ensure proper gasket sealing and torque to spec
Alternate / Superseded Part Numbers
OEM Cross References
- Yamaha:
- 6L2-W0078-00-00
- 6L2-W0078-A1-00
Aftermarket Cross References
- Mallory: 9-45606
- GLM: 12035
Shipping
Shipping: Ships same or next day for fast Canada wide shipping. ⚓
💡 Parts Desk Insight
This kit is commonly confused with smaller 9.9/15HP kits — they are NOT interchangeable.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.