Sierra Impeller 18-3065 (AP-2174) – Mercury / Mariner Outboard Water Pump Replacement
Free returns on all eligible orders
You have 30 days to request a return. All sale items are final sale.
The Sierra 18-3065 Impeller (AP-2174) is a high-quality raw water pump impeller designed for Mercury and Mariner outboards. This impeller is responsible for circulating cooling water through the engine, helping maintain proper operating temperature and preventing overheating.
Constructed from durable, flexible rubber and engineered to meet or exceed OEM specifications, this impeller ensures consistent water flow and long service life in both freshwater and saltwater environments.
Ideal for routine maintenance, replacing your impeller helps restore full cooling system efficiency and protects 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:
- 20 HP
- 25 HP
- 30 HP
➡️ Fits select 2-stroke and early 4-stroke Mercury/Mariner outboards using compatible pump housings.
Serial Number Fitment Notice
Fitment depends on:
- Engine model and year
- Water pump housing type
- Shaft spline/key configuration
⚠️ Always confirm using:
- Engine serial number
- OEM part number match (18-3065 / AP-2174)
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 with correct vane rotation
- Inspect pump housing and wear plate
- Ensure proper key or spline alignment
- Replace seals/gaskets if worn
Alternate / Superseded Part Numbers
OEM Cross References
- Mercury: 47-89984, 89984T, 89984T1
Aftermarket Cross References
- Sierra: 18-3065
- Mallory: 9-45603
- GLM: 12019
Shipping
Shipping: Ships same or next day for fast Canada wide shipping. ⚓
💡 Parts Desk Insight
If your engine is running a little warmer than usual or the telltale stream looks weaker, the impeller is often the cause. They wear gradually and can fail under load before showing obvious signs.
Replacing it regularly is one of the simplest ways to keep your outboard reliable and ready to go 👍
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.