Sierra 3090 Johnson/Evinrude Impeller

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 26 HP, mid-1970s to 1990), so always cross-reference the full model number, production year, and gearcase configuration before ordering.

Replace every 23 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. 19851990
• 4 HP models, approx. 19761980 (90-degree gearcase)
• 6 HP models, approx. 1979
• Additional 1.26 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 4075HP
• Sierra Marine Water Pump Kit 18-3390 Johnson/Evinrude 85300HP V4/V6

Always confirm fitment against your engine service manual and full model/year before ordering.