Water Pump Repair Kit – Fits Mercury/Tohatsu 9.9, 10, 15, 20 HP EFI (Replaces 8M0135821, 8M0137849)
Water Pump Repair Kit – Fits Mercury/Tohatsu 9.9, 10, 15, 20 HP EFI (Replaces 8M0135821, 8M0137849) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Water Pump Repair Kit – Fits Mercury/Tohatsu 9.9, 10, 15, 20 HP EFI...
Product Details
This complete Water Pump Repair Kit provides everything needed to restore the cooling system on Mercury, Tohatsu, and Nissan 9.9 HP to 20 HP 4-Stroke EFI outboard motors (2014 and newer, S/N 0R833820+). Engineered for a precise fit, it ensures your engine maintains optimal temperature and performance.
It is a direct replacement for Mercury part numbers 98-8M0135821, 8M0137849, 8M0134484, 46-8M0122064, and Tohatsu/Nissan equivalents 3RS-87322-1 and 3RS-87322.
- Designed for direct, hassle-free installation with all necessary gaskets included.
- Features a durable marine-grade nylon housing for longevity in saltwater and freshwater environments.
- Complete assembly includes both upper and lower housings, impeller, and seals.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 98-8M0135821 |
| Mercury | 8M0137849 |
| Mercury | 8M0134484 |
| Mercury | 46-8M0122064 |
| Tohatsu/Nissan | 3RS-87322-1 |
| Tohatsu/Nissan | 3RS-87322 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This kit is verified for Mercury Marine 4-stroke EFI models from 2014 onward with serial numbers 0R833820 and higher.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | Outboard | 9.9 | 4-Stroke EFI | 2014+ | 98-8M0135821 | S/N 1R00814+ |
| Mercury | Outboard | 10 | 4-Stroke EFI | 2014+ | 98-8M0135821 | S/N 0R833820+ |
| Mercury | Outboard | 15 | 4-Stroke EFI | 2014+ | 98-8M0135821 | S/N 0R833820+ |
| Mercury | Outboard | 20 | 4-Stroke EFI | 2014+ | 98-8M0135821 | S/N 0R833820+ |
Also compatible with select Tohatsu and Nissan MFS series engines. Please verify your model and part number.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. |
|---|---|---|---|---|---|
| Tohatsu | MFS15E | 15 | 4-Stroke | 3RS-87322-1 | |
| Tohatsu | MFS20E | 20 | 4-Stroke | 3RS-87322-1 | |
| Nissan | MFS15 | 15 | 4-Stroke | 3RS-87322-1 | |
| Nissan | MFS20 | 20 | 4-Stroke | 3RS-87322-1 |
Technical Specs
- Product Type
- Water Pump Repair Kit
- Installation
- Direct replacement with gaskets included
- Housing Material
- Marine Grade Nylon
- Housing Color
- Black
- Dimensions
- Height: 16.0, Width: 11.5, Length: 11.5
- Weight
- 0.63 lb (0.29 kg)
- Other Technical Attributes
- Complete kit with both upper and lower housings
What’s in the Box
- 1 x Impeller (334-65021 / 3LD-65021)
- 1 x Housing
- 1 x Insert Cup
- 1 x Wear Plate
- 2 x Gaskets
- 1 x Key
- 1 x Seal Kit
Installation Notes
- Disconnect the battery and shift the outboard into neutral before beginning work.
- Remove the lower unit (gearcase) from the outboard motor. Refer to your service manual for specific bolt locations.
- Unbolt and remove the old water pump housing assembly from the driveshaft.
- Clean the mating surfaces on the lower unit and inspect the driveshaft for wear or damage.
- Assemble the new impeller, key, wear plate, and housing per the included diagram or service manual. Lubricate components with marine grease.
- Slide the new water pump assembly down the driveshaft and secure it with the original bolts. Torque to factory specifications.
- Reinstall the lower unit, ensuring the driveshaft, shift shaft, and water tube are properly aligned.
- Reconnect the battery and test the engine using a water supply (flushing muffs or test tank) to confirm water is pumping correctly from the tell-tale port.
Troubleshooting & FAQ
How do I confirm this kit fits my specific engine?
The surest way is to check your engine's serial number. This kit fits Mercury 9.9-20 HP EFI models with serial number 0R833820 and up. For Tohatsu/Nissan, match your engine model (e.g., MFS15E/MFS20E) and the OEM part number 3RS-87322-1.
What are the signs of a faulty water pump?
Common symptoms include a weak or no water stream from the tell-tale (pee hole), engine overheating alarms, and in severe cases, steam from the exhaust. Reduced engine performance can also be a sign.
How often should a water pump impeller be replaced?
As a general maintenance guideline, inspect the impeller annually and replace it every 1-2 years, or every 100-200 hours of use, whichever comes first. Usage in sandy or silty water may require more frequent replacement.
Is this a complete kit or do I need other parts?
This is a complete repair kit containing the impeller, upper and lower housings, wear plate, gaskets, and seals. You should not need any other parts for a standard water pump service.
Can I just replace the impeller instead of the whole kit?
While possible, it is highly recommended to replace the entire assembly. The housing, wear plate, and seals wear out over time and can reduce the new impeller's efficiency and lifespan, leading to premature failure.
Is there a difference in performance compared to the OEM kit?
This aftermarket kit is designed to meet or exceed OEM specifications for fit, material quality, and cooling performance. When installed correctly, you can expect performance comparable to the original factory part.
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.
Payment & Security
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