Sierra 3073 Yamaha/Mercury/Mariner Impeller
Free returns on all eligible orders
You have 30 days to request a return. All sale items are final sale.
The Sierra 3073 (18-3073) Impeller is a replacement lower-unit water pump impeller for compatible Yamaha, Mercury, and Mariner 4–5 HP outboards. Six flexible blades rotate inside the pump housing to draw cooling water through the gearcase and circulate it through the engine. Replaces Yamaha 6E0-44352-00-00 and Mercury/Mariner 47-96305M.
Parts Desk Insight — Best Use
Note that 47-3073 can resemble a Mercury OEM-format number but is the distributor SKU for Sierra 18-3073. This impeller covers both Yamaha and Mercury/Mariner small-HP applications with different OEM cross-references — confirm the original impeller number from the engine parts diagram before removing the lower unit. For Yamaha, match to 6E0-44352-00-00; for Mercury/Mariner, match to 47-96305M.
Replace every 2–3 seasons or 200 hours regardless of visible wear. At only 9 grams, this is one of the smallest impellers in the Sierra J/E and Yamaha range — easy to overlook during service, but critical for engine cooling on small portable outboards.
This impeller is included in Sierra water pump kits 18-3473 and 18-48619 for a complete pump service.
Key Specifications
- Sierra part number: 18-3073
- Six flexible impeller blades
- Fits compatible Yamaha and Mercury/Mariner 4–5 HP outboards
- Included in Sierra water pump kits 18-3473 and 18-48619
- Impeller only — housing, wear plate, key, and gaskets not included
- UPC: 030999315250
Engine Compatibility
Documented applications:
- Yamaha 4 HP two-stroke: approx. 1984–1999
- Yamaha 5 HP two-stroke: approx. 1984–2002
- Mariner 4A models with 6E0 serial code
- Mariner 5C models with 6E3 serial code
- Select Mercury and Mariner 4–6 HP outboards using OEM impeller 47-96305M
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: 18-3073 / 118-3073
- Yamaha: 6E0-44352-00-00 / 6E0-44352-00
- Mercury/Mariner: 47-96305M / 96305M
- Mallory Marine: 9-45611
- GLM Marine: 89860
- Aqua Power: 2172
Installation Notes
Lower-unit removal is required to access the water pump. During service: inspect the pump housing, wear plate, 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.
Related Yamaha/Mercury Impellers
- Sierra 3042 (18-3042) Yamaha Impeller – F75/F80/F90/F100
- Sierra 3074 (18-3074) Yamaha/Mercury/Mariner Impeller – 9.9–15HP
- 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 3090 (18-3090) 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.