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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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Water Pump Impeller Repair Kit – Fits Mercury & Tohatsu 8/9.8/9...
Product Details
Restore your outboard's cooling system with this complete Water Pump Impeller Repair Kit – Fits Mercury & Tohatsu 8/9.8/9.9 HP (Replaces 803750A03, 3B2-87322-2). It is designed for Mercury 8-9.9 HP (209cc) 4-Stroke models and a wide range of Tohatsu and Nissan 8-9.8 HP 4-Stroke outboards, including the MFS8, MFS9.8, NSF8, and NSF9.8 series.
This kit serves as a direct interchange for Mercury part numbers 46-803750A03, 803750A03, 80375A03, 803748Q01, and 803748K01, as well as Tohatsu/Nissan legacy numbers 3B2-87322-0, 3B2-87322-1, 3B2-87322-2 and modern equivalents 3B2873220M, 3B2873221M, and 3B2873222M.
- Engineered as a direct-fit replacement for straightforward installation.
- Features a durable marine-grade CR-Neoprene impeller with a nylon hub for longevity.
- Includes a stainless steel wear plate, liner, gaskets, and all necessary bolts for a complete service.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Superseded By | Notes |
|---|---|---|---|
| Mercury | 46-803750A03 | Primary replacement number. | |
| 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 | Original part number. |
| Tohatsu / Nissan | 3B2-87322-1 | 3B2-87322-2 | Superseded part. |
| Tohatsu / Nissan | 3B2-87322-2 | 3B2873222M | Current OEM part number. |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Mercury models, compatibility is often determined by serial number. Please verify your engine's serial falls within the specified ranges.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | 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 & Up | 803750A03 | 209cc models |
| Mercury | 8 HP | 8 | 4-Stroke | 0P325500 & Up | 803750A03 | 209cc models |
| Mercury | 8 HP | 8 | 4-Stroke | 0R042475 & Up | 803750A03 | 209cc models |
| Mercury | 9.8 HP | 9.8 | 4-Stroke | 0N007788-0N055109 | 803750A03 | |
| Mercury | 9.8 HP | 9.8 | 4-Stroke | 0N055110 & Up | 803750A03 | |
| Mercury | 9.9 HP | 9.9 | 4-Stroke | 0N260037 & Up | 803750A03 | |
| Mercury | 9.9 HP | 9.9 | 4-Stroke | 0P325500 & Up | 803750A03 | |
| Mercury | 9.9 HP | 9.9 | 4-Stroke | 0R042475 & Up | 803750A03 |
This kit fits various Tohatsu 2-stroke and 4-stroke models. The part number evolution from 3B2-87322-0 to 3B2873222M ensures broad compatibility.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Tohatsu | M8B | 8 | 2-Stroke | 3B2-87322-0 | Superseded to 3B2873222M | |
| Tohatsu | M9.8B | 9.8 | 2-Stroke | 3B2-87322-0 | Superseded to 3B2873222M | |
| Tohatsu | MFS8A | 8 | 4-Stroke | 3B2873222M | Including MFS8A2, MFS8A3 | |
| Tohatsu | MFS8A2 | 8 | 4-Stroke | 2004 | 3B2873222M | |
| Tohatsu | MFS8A3 | 8 | 4-Stroke | 2003–2014 | 3B2873222M | |
| Tohatsu | MFS9.8A | 9.8 | 4-Stroke | 3B2873222M | Including MFS9.8A2, MFS9.8A3 | |
| Tohatsu | MFS9.8A2 | 9.8 | 4-Stroke | 2004 | 3B2873222M | |
| Tohatsu | MFS9.8A3 | 9.8 | 4-Stroke | 2003–2014 | 3B2873222M |
Nissan outboards often share components with Tohatsu engines of the same class. This kit is compatible with the following Nissan models.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Nissan | NS8B | 8 | 2-Stroke | 3B2-87322-0 | Superseded to 3B2873222M | |
| Nissan | NS9.8B | 9.8 | 2-Stroke | 3B2-87322-0 | Superseded to 3B2873222M | |
| Nissan | NSF8A | 8 | 4-Stroke | 3B2873222M | Including NSF8A2, NSF8A3 | |
| Nissan | NSF8A2 | 8 | 4-Stroke | 2004 | 3B2873222M | |
| Nissan | NSF8A3 | 8 | 4-Stroke | 2003–2014 | 3B2873222M | |
| Nissan | NSF9.8A | 9.8 | 4-Stroke | 3B2873222M | Including NSF9.8A2, NSF9.8A3 | |
| Nissan | NSF9.8A2 | 9.8 | 4-Stroke | 2004 | 3B2873222M | |
| Nissan | NSF9.8A3 | 9.8 | 4-Stroke | 2003–2014 | 3B2873222M |
Technical Specs
- Product Type
- Water Pump Impeller Repair Kit
- Installation
- Direct replacement
- Housing Material
- Stainless Steel (wear plate & liner)
- Impeller Material
- Marine Grade CR-Neoprene with Nylon Hub
- Weight
- 0.14 kg (0.31 lbs)
- Number of Blades
- 6
- Internal Hub/Shaft Size
- 12 mm (0.472 inch)
- Outer Diameter
- 40.3 mm (1.587 inch)
- Impeller Height/Thickness
- 18 mm (0.709 inch)
What’s in the Box
- 1 x Water Pump Impeller (8037481)
- 1 x Driveshaft Pin (9521811)
- 1 x Insert Cup (8037511)
- 1 x Wear Plate (8037531)
- 1 x Gasket (8M0072139)
- 1 x Gasket (8M0072138)
- 1 x Gasket (8M0072137)
- 4 x Bolts and Washers (879194305)
Installation Notes
- Disconnect the spark plug wire and shift the outboard into neutral.
- Remove the lower unit bolts and carefully separate the lower unit from the upper casing.
- Unbolt and remove the water pump housing to access the old impeller.
- Take note of the old impeller's blade orientation before removing it and the driveshaft key.
- Clean all surfaces of the housing, wear plate, and insert cup, removing any old gasket material or debris.
- Install the new gaskets, wear plate, and insert cup into the housing.
- Slide the new impeller onto the driveshaft while turning the shaft clockwise to bed the vanes correctly.
- Reassemble the water pump housing, ensuring a proper seal. Torque bolts to manufacturer specs.
- Reattach the lower unit, ensuring the water tube and driveshaft align correctly.
Troubleshooting & FAQ
How do I confirm this kit fits my specific engine?
The most reliable way is to match your engine's model, year, and serial number against the compatibility tables above. If your OEM part number is listed in our Part Number Matrix (e.g., 46-803750A03 or 3B2-87322-2), this kit is a confirmed fit.
What are the signs of a failing water pump impeller?
Common symptoms include a weak or non-existent "telltale" water stream, engine overheating alarms, and reduced engine performance. Visible signs on the old impeller include cracked, brittle, or missing vanes and a glazed or melted appearance.
How often should I replace my impeller?
For preventative maintenance, it's recommended to replace the impeller every 1-2 years or every 100-200 hours of use, whichever comes first. Usage in saltwater or sandy/silty conditions may require more frequent inspections and replacements.
Is there a difference in installing this on a 2-stroke vs. a 4-stroke model?
The fundamental process of accessing and replacing the impeller in the lower unit is very similar for both 2-stroke and 4-stroke engines listed. However, torque specifications for bolts and specific disassembly steps may vary. Always consult a service manual for your specific engine model if unsure.
What happens if I install the impeller with the vanes facing the wrong direction?
Installing the impeller with its vanes curved in the opposite direction of the driveshaft's rotation will result in poor water flow and will cause the pump to fail, leading to rapid engine overheating. The vanes should curve back, opposite to the direction of rotation.
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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