Water Pump Impeller – Fits Evinrude Johnson 2–6 HP (Replaces 387361, 763735)
Water Pump Impeller – Fits Evinrude Johnson 2–6 HP (Replaces 387361, 763735) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
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Water Pump Impeller – Fits Evinrude Johnson 2–6 HP (Replaces 387361...
Product Details
This Water Pump Impeller – Fits Evinrude Johnson 2–6 HP (Replaces 387361, 763735) is designed for select Evinrude and Johnson outboard engines, including 2 HP models from 1985–1990, 4 HP models from 1976–1980 (with the 90-degree gearcase), and 6 HP models from 1979. It features a six-blade rubber design with a durable brass insert to ensure reliable performance within your engine's cooling system.
This part serves as a direct replacement for Johnson/Evinrude parts 387361, 763735, and 777831, as well as Sierra 18-3090 and Mallory 9-45210.
- Engineered for direct OEM-equivalent installation.
- Constructed from durable rubber with a brass center insert for longevity.
- Designed to restore cooling system efficiency and prevent overheating.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Johnson/Evinrude | 387361 |
| Johnson/Evinrude | 763735 |
| Johnson/Evinrude | 777831 |
| Sierra | 18-3090 |
| Mallory | 9-45210 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Johnson/Evinrude/OMC engines, pay close attention to the specific model notes, such as gearcase type, as fitment can vary.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Johnson/Evinrude | 2 Jr, Colt | 2 HP | 2-Stroke | 1985–1990 | 387361, 763735 | |
| Johnson/Evinrude | Outboard | 4 HP | 2-Stroke | 1976–1980 | 387361, 763735 | 90 degree gearcase only |
| Johnson/Evinrude | Outboard | 6 HP | 2-Stroke | 1979 | 387361, 763735 |
Technical Specs
- Product Type
- Water Pump Impeller
- Installation
- Direct OEM replacement
- Housing Material
- Rubber with brass insert
- Dimensions
- 38.27–38.8 mm external diameter × 17.82–18.6 mm height (1.5 inch diameter)
- Weight
- 33–40 g
- Number of Blades
- 6
- Internal Shaft Insert Diameter
- 11.2–11.23 mm
- Other Technical Attributes
- Brass center insert for durability
What’s in the Box
- 1 x Water Pump Impeller (387361/763735)
- 1 x Key (included with some versions)
Installation Notes
- Disconnect the engine's battery and shift the outboard into neutral.
- Remove the bolts securing the lower unit (gearcase) and carefully separate it from the upper housing.
- Locate the water pump housing on top of the gearcase and unbolt it.
- Slide the housing up the driveshaft to expose the old impeller. Note the direction of the blades.
- Remove the old impeller. You may need to pry it gently. Remove the old drive key from the shaft.
- Clean any debris or corrosion from the pump housing, wear plate, and driveshaft.
- Install the new drive key into the slot on the driveshaft.
- Slide the new impeller onto the driveshaft, aligning the keyway. Rotate the driveshaft clockwise while pushing down to bend the blades in the correct direction.
- Apply a light coat of marine grease or soapy water to the inside of the pump housing and reinstall it over the impeller.
- Secure the housing bolts, reinstall the lower unit, and reconnect the battery. Test the cooling system before extensive use.
Troubleshooting & FAQ
How do I know if my water pump impeller is failing?
Common signs of a worn or damaged impeller include a weak or intermittent water stream from the tell-tale outlet, engine overheating alarms, or a noticeable decrease in cooling performance. A visual inspection during routine maintenance is the best way to confirm its condition.
Will this fit my 4 HP Johnson if I don't know the gearcase type?
This impeller is only compatible with the 4 HP models from 1976-1980 that have a 90-degree gearcase. We strongly recommend verifying your gearcase type before purchasing to ensure compatibility. If unsure, consult your service manual or a qualified marine mechanic.
Why is there a range in the dimensions and weight?
The slight variations in measurements (e.g., 38.27 mm vs 38.8 mm diameter) come from different aftermarket data sources. These minor differences are within manufacturing tolerances and do not affect fitment or performance for the specified compatible models.
What is the recommended replacement interval for an impeller?
For most outboard engines, it is recommended to inspect the impeller annually and replace it every 1-2 years, or every 100-200 hours of operation, whichever comes first. This interval can be shorter if you frequently operate in sandy, silty, or saltwater environments.
Is the key always included?
The package contents note that a key is included with some versions. While most kits contain one, we recommend retaining your original key during replacement just in case it is needed.
What causes premature impeller failure?
The most common cause is running the engine dry, even for a few seconds, which can overheat and damage the rubber blades. Other causes include debris ingestion, chemical degradation from fuel or oil, and normal wear and tear over time.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
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