Sierra 3090 Johnson/Evinrude Impeller
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The Sierra 3090 (18-3090) Impeller is a replacement water pump impeller for compatible Johnson, Evinrude, and OMC small-horsepower outboards. Installed inside the lower-unit water pump, its six flexible blades draw cooling water into the engine to maintain proper operating temperature. Replaces OEM numbers 387361 and 763735 and is specifically designed for applications using the later plastic water pump housing.
Parts Desk Insight — Best Use
The critical distinction with the 18-3090 is the plastic pump housing requirement. Matching by horsepower alone will lead to the wrong impeller — verify the OEM impeller number and confirm the plastic housing before opening the lower unit. This impeller fits a narrow band of small J/E outboards (primarily 2–6 HP, mid-1970s to 1990), so always cross-reference the full model number, production year, and gearcase configuration before ordering.
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.
Key Specifications
- Sierra part number: 18-3090
- Six flexible impeller blades
- Designed for plastic water pump housings
- Approximate diameter: 1.52 in
- Approximate thickness: 0.72 in
- Approximate shaft bore: 0.44 in
- Impeller only — housing, plate, key, and seals not included
- UPC: 808282235000
Engine Compatibility
Confirmed applications include compatible Johnson and Evinrude outboards:
- 2 HP models, approx. 1985–1990
- 4 HP models, approx. 1976–1980 (90-degree gearcase)
- 6 HP models, approx. 1979
- Additional 1.2–6 HP applications using OEM impeller 387361 or 763735
Exact fitment depends on model number, production year, gearcase, and water pump housing type. Do not order by horsepower alone.
Fitment Verification Checklist
- Complete outboard model number and production year
- Gearcase configuration
- Plastic water pump housing confirmed
- OEM impeller number: 387361, 0387361, 763735, or 0763735
- Impeller dimensions and shaft/drive-key configuration
Alternate Part Numbers
- Sierra: 18-3090 / 118-3090
- Johnson/Evinrude/OMC: 387361, 0387361, 763735, 0763735
- Mallory Marine: 9-45210
- GLM: 89490
- CEF: 500358
Installation Notes
The lower unit must be removed to access the water pump. During service: inspect the housing, wear plate, key, seals, and driveshaft; remove any broken impeller fragments from cooling passages; lubricate the new impeller with clean soapy water or approved lubricant; rotate the driveshaft in its normal direction while seating the housing over the blades. Test for a strong cooling-water telltale before operating under load. Never run the outboard without an adequate cooling-water supply.
Related J/E Impellers
- Sierra 3050 (18-3050) Johnson/Evinrude Impeller
- Sierra 3051 (18-3051) Johnson/Evinrude Impeller
- Sierra 3001 Johnson/Evinrude Impeller
- Sierra 3002 Johnson/Evinrude Impeller
- Sierra 3043 Johnson/Evinrude Impeller
- Sierra 3055 Johnson/Evinrude Impeller
- Sierra 3058 Johnson/Evinrude Impeller
- Sierra 3059 Johnson/Evinrude Impeller
- Sierra 3083 Johnson/Evinrude Impeller
- Sierra 31041 Johnson/Evinrude Impeller
Compatible Water Pump Kits
- Sierra Marine Water Pump Kit 18-3380 – Johnson/Evinrude 40–75HP
- Sierra Marine Water Pump Kit 18-3390 – Johnson/Evinrude 85–300HP V4/V6
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.