Water Pump Impeller Repair Kit – Fits Mercury & Tohatsu 8/9.8/9.9 HP (Replaces 803750A03, 3B2-87322-2)
Water Pump Impeller Repair Kit – Fits Mercury & Tohatsu 8/9.8/9.9 HP (Replaces 803750A03, 3B2-87322-2) is backordered and will ship as soon as it is back in stock.
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Water Pump Impeller Repair Kit – Fits Mercury & Tohatsu 8/9.8/9...
Water Pump Impeller Repair Kit – Fits Mercury & Tohatsu 8/9.8/9.9 HP (Replaces 803750A03, 3B2-87322-2) is backordered and will ship as soon as it is back in stock.
Product Details
Restore your outboard’s cooling system with this complete water pump impeller repair kit for selected Mercury, Tohatsu, and Nissan 8–9.9 HP outboards. The kit is intended for Mercury 8–9.9 HP 209cc 4-stroke models and selected Tohatsu and Nissan 8–9.8 HP outboards, including MFS8, MFS9.8, NSF8, and NSF9.8 series applications. Always compare your engine model, stroke, serial number, and original part number before ordering.
This kit is listed as an aftermarket replacement for Mercury references 46-803750A03, 803750A03, 80375A03, 803748Q01, and 803748K01. Tohatsu and Nissan legacy references include 3B2-87322-0, 3B2-87322-1, and 3B2-87322-2, with modern references including 3B2873220M, 3B2873221M, and 3B2873222M.
- Complete water pump service kit for the listed applications.
- Marine-grade CR-neoprene impeller with nylon hub.
- Includes the wear plate, insert cup, gaskets, driveshaft pin, bolts, and washers shown in the package list.
- Designed as a direct replacement when the listed engine and part-number conditions match.
Part Number Matrix
The following references are provided for cross-reference purposes. A matching number should still be checked against the complete engine application.
| Brand | Part Number | Superseded By | Notes |
|---|---|---|---|
| Mercury | 46-803750A03 | Primary replacement reference. | |
| Mercury | 803750A03 | 46-803750A03 | Alternate reference. |
| Mercury | 80375A03 | 46-803750A03 | Alternate reference. |
| Mercury | 803748Q01 | 46-803750A03 | Alternate reference. |
| Mercury | 803748K01 | 46-803750A03 | Alternate reference. |
| Tohatsu / Nissan | 3B2-87322-0 | 3B2-87322-1 | Legacy reference. |
| Tohatsu / Nissan | 3B2-87322-1 | 3B2-87322-2 | Superseded reference. |
| Tohatsu / Nissan | 3B2-87322-2 | 3B2873222M | Current-style reference shown for cross-reference. |
Engine & Model Compatibility
Compatibility depends on the complete engine configuration. For Mercury applications, verify the engine serial number against the applicable range. For Tohatsu and Nissan applications, verify the exact model suffix and stroke before installation.
| Brand | Model | Rated HP | Stroke | Serial / Year Range | OEM Reference | Notes |
|---|---|---|---|---|---|---|
| Mercury | 8 HP | 8 | 4-Stroke | 0N014717–0N055109 | 803750A03 | 209cc models |
| Mercury | 8 HP | 8 | 4-Stroke | 0N027903–0N055109 | 803750A03 | 209cc models |
| Mercury | 8 HP | 8 | 4-Stroke | 0N055110 and up | 803750A03 | 209cc models |
| Mercury | 8 HP | 8 | 4-Stroke | 0P325500 and up | 803750A03 | 209cc models |
| Mercury | 8 HP | 8 | 4-Stroke | 0R042475 and up | 803750A03 | 209cc models |
| Mercury | 9.8 HP | 9.8 | 4-Stroke | 0N007788–0N055109 | 803750A03 | |
| Mercury | 9.8 HP | 9.8 | 4-Stroke | 0N055110 and up | 803750A03 | |
| Mercury | 9.9 HP | 9.9 | 4-Stroke | 0N260037 and up | 803750A03 | |
| Mercury | 9.9 HP | 9.9 | 4-Stroke | 0P325500 and up | 803750A03 | |
| Mercury | 9.9 HP | 9.9 | 4-Stroke | 0R042475 and up | 803750A03 |
The cross-reference list also includes selected Tohatsu and Nissan 2-stroke and 4-stroke models. The model, stroke, and applicable part-number conditions must match together.
| Brand | Model | Rated HP | Stroke | Years | OEM Reference | Notes |
|---|---|---|---|---|---|---|
| Tohatsu | M8B | 8 | 2-Stroke | 3B2-87322-0 | Legacy reference; verify replacement number. | |
| Tohatsu | M9.8B | 9.8 | 2-Stroke | 3B2-87322-0 | Legacy reference; verify replacement number. | |
| Tohatsu | MFS8A / MFS8A2 / MFS8A3 | 8 | 4-Stroke | 2003–2014 where applicable | 3B2873222M | Verify exact suffix. |
| Tohatsu | MFS9.8A / MFS9.8A2 / MFS9.8A3 | 9.8 | 4-Stroke | 2003–2014 where applicable | 3B2873222M | Verify exact suffix. |
| Nissan | NS8B | 8 | 2-Stroke | 3B2-87322-0 | Legacy reference; verify replacement number. | |
| Nissan | NS9.8B | 9.8 | 2-Stroke | 3B2-87322-0 | Legacy reference; verify replacement number. | |
| Nissan | NSF8A / NSF8A2 / NSF8A3 | 8 | 4-Stroke | 2003–2014 where applicable | 3B2873222M | Verify exact suffix. |
| Nissan | NSF9.8A / NSF9.8A2 / NSF9.8A3 | 9.8 | 4-Stroke | 2003–2014 where applicable | 3B2873222M | Verify exact suffix. |
Technical Specifications
- Product Type
- Water pump impeller repair kit
- Installation
- Direct replacement when application conditions match
- Housing Components
- Stainless steel wear plate and insert cup
- Impeller Material
- Marine-grade CR-neoprene with nylon hub
- Weight
- 0.14 kg (0.31 lb)
- Number of Blades
- 6
- Internal Hub / Shaft Size
- 12 mm (0.472 in)
- Outer Diameter
- 40.3 mm (1.587 in)
- Impeller Height / Thickness
- 18 mm (0.709 in)
What’s in the Box
- 1 × Water pump impeller (8037481)
- 1 × Driveshaft pin (9521811)
- 1 × Insert cup (8037511)
- 1 × Wear plate (8037531)
- 1 × Gasket (8M0072139)
- 1 × Gasket (8M0072138)
- 1 × Gasket (8M0072137)
- 4 × Bolts and washers (879194305)
Installation Notes
- Disconnect the spark-plug wire and place the outboard in neutral.
- Remove the lower-unit bolts and carefully separate the lower unit from the upper casing.
- Remove the water-pump housing to access the existing impeller.
- Note the existing vane orientation before removing the impeller and driveshaft pin.
- Clean the housing, wear plate, insert cup, and sealing surfaces. Remove old gasket material and debris.
- Install the new gaskets, wear plate, and insert cup in the correct positions.
- Install the new impeller while turning the driveshaft in the correct direction so the vanes seat properly.
- Reassemble the water-pump housing and tighten the fasteners to the manufacturer’s specifications.
- Reinstall the lower unit, confirming proper alignment of the water tube and driveshaft.
- After installation, run the engine according to the service-manual procedure and confirm a normal cooling-water telltale stream.
Troubleshooting & FAQ
How do I confirm this kit fits my engine?
Match the engine brand, exact model, horsepower, stroke, serial number or year range, and original part number against the information above. A listed reference such as 46-803750A03 or 3B2-87322-2 should be checked together with the complete engine application.
What are the signs of a failing water-pump impeller?
Typical symptoms include a weak or missing telltale stream, overheating warnings, and reduced cooling performance. The removed impeller may have cracked, brittle, missing, distorted, or glazed vanes.
How often should the impeller be replaced?
Replacement intervals depend on the engine manufacturer, operating hours, water conditions, and inspection results. Saltwater, sand, silt, and extended storage can increase wear, so inspect and replace the impeller according to the service manual.
Is installation different on a 2-stroke and 4-stroke model?
The basic lower-unit water-pump service is similar, but disassembly steps, fastener locations, torque values, and alignment procedures can vary. Use the service manual for the specific engine.
What happens if the impeller vanes are installed incorrectly?
Incorrect vane orientation can reduce water flow and may cause rapid overheating. Install the impeller in the orientation specified by the engine service manual and rotate the driveshaft as required during assembly.
Is this an OEM component?
No. This listing is for an aftermarket replacement kit intended to match the listed applications and reference numbers. It is not supplied as an OEM-branded component.
How quickly is the order shipped?
Typical transit is 5–15 days for standard worldwide shipping. Available expedited options and final delivery estimates are shown at checkout where applicable.
What is the warranty and return policy?
The kit is covered by a 1-year warranty against manufacturing defects under normal use. Returns are accepted within the applicable standard return period when the item is unused and in its original condition. Contact support for order-specific instructions.
Safety & Important Information
- Verify the engine model, stroke, serial number or year range, and original part before ordering.
- Compare the supplied components with the original parts before installation. Do not install the kit if the dimensions or components differ.
- This is an aftermarket replacement, not an OEM component.
- Follow the engine manufacturer’s service manual for torque values, seal orientation, alignment, and testing.
- Professional installation is recommended when lower-unit service experience or the correct service information is unavailable.
About Sea Sierra
- Pro-Grade Standards: Marine replacement parts selected for dependable performance in real-world service conditions.
- Fast Global Fulfillment: Standard delivery is available to most regions, with delivery estimates shown at checkout.
- Manufacturer-Direct Value: Practical aftermarket replacement parts at competitive pricing.
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