Sierra Impeller 18-3056 (AP-1814) – Mercury / Mariner Outboard Water Pump Replacement
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You have 30 days to request a return. All sale items are final sale.
The Sierra 18-3056 Impeller (AP-1814) is a direct replacement raw water pump impeller designed for Mercury and Mariner outboards. This impeller is responsible for circulating cooling water through the engine, ensuring proper temperature control and preventing overheating.
Built to meet or exceed OEM specifications, this impeller features durable, flexible rubber vanes and a precision-fit hub for reliable performance in both freshwater and saltwater environments.
Routine replacement of the impeller is essential to maintain optimal cooling efficiency and protect your engine from heat-related damage.
Key Features
- Direct replacement raw water pump impeller
- Flexible rubber vanes for efficient water flow
- Precision-fit hub for secure installation
- Maintains proper engine cooling performance
- Marine-grade construction for durability
- Sierra limited lifetime warranty
Engine Compatibility
Mercury / Mariner Outboards
Commonly used on:
- 25 HP
- 30 HP
- 35 HP
➡️ Fits select Mercury/Mariner 2-stroke outboards using compatible water pump assemblies.
Serial Number Fitment Notice
Fitment depends on:
- Engine model and year
- Water pump housing design
- Shaft configuration (keyed vs splined)
⚠️ Always confirm using:
- Engine serial number
- OEM part number match (18-3056 / AP-1814)
When This Part Needs Replacement
Replace the impeller if you notice:
- Weak or no telltale stream
- Engine overheating
- Reduced cooling performance
- Cracked, hardened, or missing vanes
- After seasonal storage
Recommended service interval: every 100 hours or annually
Installation Notes
- Lubricate impeller before installation
- Install vanes in correct rotation direction
- Inspect housing and wear plate
- Ensure proper hub alignment (key or spline)
- Replace seals or gaskets if worn
Alternate / Superseded Part Numbers
OEM Cross References
- Mercury: 47-89982, 89982T, 89982T1
Aftermarket Cross References
- Sierra: 18-3056
- Mallory: 9-45604
- GLM: 12016
Shipping
Shipping: Ships same or next day for fast Canada wide shipping. ⚓
💡 Parts Desk Insight
A worn impeller can still move water at idle but fail when you increase throttle. If your engine runs hotter at speed, this is often the cause.
Replacing it regularly is a simple way to keep your outboard running cool and avoid unexpected breakdowns 👍
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.