Sierra 3074 Yamaha/Mercury/Mariner Impeller
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The Sierra 3074 (18-3074) Impeller is a six-blade replacement water pump impeller for compatible Yamaha, Mercury, and Mariner 9.9–15 HP outboards. Installed inside the lower-unit water pump, it draws cooling water through the gearcase and circulates it through the engine to maintain proper operating temperature.
Parts Desk Insight — Best Use
Note that 47-3074 can look like a Mercury OEM-format number but is the distributor SKU for Sierra 18-3074. This impeller spans two engine brands (Yamaha and Mercury/Mariner) with different OEM cross-references — confirm the original impeller number from the engine parts diagram before removing the lower unit. For Yamaha, match to the 682-series number; for Mercury/Mariner, match to 47-84027M, 47-84027T, or 47-96619M.
Replace every 2–3 seasons or 200 hours regardless of visible wear. Impeller vanes harden and lose flexibility before showing obvious damage, reducing cooling flow without warning.
This impeller is included in Sierra water pump kits 18-3148 and 18-3411 for a complete pump service.
Key Specifications
- Sierra part number: 18-3074
- Six flexible impeller blades
- Fits compatible Yamaha and Mercury/Mariner 9.9–15 HP outboards
- Included in Sierra water pump kits 18-3148 and 18-3411
- Impeller only — housing, wear plate, key, and gaskets not included
- UPC: 030999315267
Engine Compatibility
Documented Yamaha applications (682-series water pump impeller):
- Yamaha 9.9D two-stroke: approx. 1984–1995
- Yamaha 15D two-stroke: approx. 1984–1995
- Yamaha F9.9A four-stroke: approx. 1985–2004
- Yamaha F9.9B four-stroke: approx. 1985–1996
- Yamaha FT9.9 four-stroke: approx. 1985–1990
- Yamaha T9.9 four-stroke: approx. 1985–2003
Also cross-referenced to select Mercury and Mariner 9.9–15 HP applications using OEM numbers 47-84027M, 47-84027T, or 47-96619M.
Always confirm by complete engine model number, production year, gearcase configuration, and OEM parts diagram. Do not order by horsepower alone.
Alternate Part Numbers
- Sierra: 18-3074 / 118-3074
- Yamaha: 682-44352-00-00, 682-44352-01-00, 682-44352-03-00, 682-44352-40-00
- Mercury/Mariner: 47-84027M, 47-84027T, 47-96619M
- Quicksilver: 8M6013999
- Mallory Marine: 9-45605
- GLM Marine: 89880
Installation Notes
Lower-unit removal is required to access the water pump assembly. During service: inspect the housing, wear plate, cup, key, and seals; remove any broken impeller fragments from cooling passages; lubricate the new impeller with clean soapy water or approved assembly lubricant; rotate the driveshaft in its normal operating direction while seating the housing over the blades. Confirm strong cooling-water telltale flow before operating under load. Never operate the outboard without an adequate cooling-water supply.
Compatible Water Pump Kits
Related Yamaha Impellers
- Sierra 3042 (18-3042) Yamaha Impeller
- Sierra Impeller 18-3086 – Yamaha Outboard Water Pump Replacement
Related J/E Impellers
- Sierra 3050 (18-3050) Johnson/Evinrude Impeller
- Sierra 3051 (18-3051) Johnson/Evinrude Impeller
- Sierra 3083 (18-3083) Johnson/Evinrude Impeller
Always confirm fitment against your engine service manual and full model/year before ordering.
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.