Water Pump Impeller Repair Kit – Fits Mercury/Tohatsu 9.9-20 HP 4-Stroke EFI (Replaces 8M0137849, 8M0135821)
Water Pump Impeller Repair Kit – Fits Mercury/Tohatsu 9.9-20 HP 4-Stroke EFI (Replaces 8M0137849, 8M0135821) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
Worry-free returns
You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).
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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 9.9-20 HP 4-S...
Product Details
This Water Pump Impeller Repair Kit – Fits Mercury/Tohatsu 9.9-20 HP 4-Stroke EFI (Replaces 8M0137849, 8M0135821) is designed for Mercury/Mariner 9.9, 10, 15, and 20 HP 4-Stroke EFI outboards (2020 and newer, S/N 0R833820+) and compatible Tohatsu/Nissan 15-20 HP (MFS) 4-Stroke models. It provides all necessary components to restore your engine's cooling system performance.
It serves as a direct interchange for Mercury part numbers 8M0137849, 8M0135821, 98-8M0135821, 8M0134484, 46-8M0122064, and Tohatsu 3RS-87322-1.
- Designed for direct replacement of OEM parts, ensuring a precise fit.
- Constructed with a marine-grade nylon housing and a durable CR-Neoprene impeller for longevity.
- Includes a complete set of gaskets, seals, and hardware for a comprehensive overhaul.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 8M0137849 |
| Mercury | 8M0135821 |
| Mercury | 98-8M0135821 |
| Mercury | 8M0134484 |
| Mercury | 46-8M0122064 |
| Tohatsu | 3RS-87322-1 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Mercury and Mariner outboards, this kit fits specific 4-stroke EFI models from 2020 onward with serial number 0R833820 and up. Ensure your S/N matches before ordering.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | 9.9 HP EFI | 9.9 | 4-Stroke | 2020+ | 8M0135821/8M0137849 | S/N 0R833820 and above |
| Mercury | 10 HP EFI | 10 | 4-Stroke | 2020+ | 8M0135821/8M0137849 | S/N 0R833820 and above |
| Mercury | 15 HP EFI | 15 | 4-Stroke | 2020+ | 8M0135821/8M0137849 | S/N 0R833820 and above |
| Mercury | 20 HP EFI | 20 | 4-Stroke | 2020+ | 8M0135821/8M0137849 | S/N 0R833820 and above |
| Mercury | ProKicker | 9.9-20 | 4-Stroke | 2020+ | 8M0135821/8M0137849 | 333cc, 2-cylinder variants |
| Mercury | SeaPro | 9.9-20 | 4-Stroke | 2020+ | 8M0135821/8M0137849 | 333cc, 2-cylinder variants |
For Tohatsu and Nissan, this kit is listed as a cross-reference. Verify your engine uses a compatible cooling system design before purchasing.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Tohatsu | MFS | 15 | 4-Stroke | 3RS-87322-1 | Cross-reference only | |
| Tohatsu | MFS | 20 | 4-Stroke | 3RS-87322-1 | Cross-reference only | |
| Nissan | 15-20 | 4-Stroke | 3RS-87322-1 | Cross-reference only |
Technical Specs
- Product Type
- Water Pump Impeller Repair Kit
- Installation
- Direct replacement for OEM parts
- Housing Material
- Marine Grade Nylon Water Pump Housing with SS316 Wear Plate & Liner
- Housing Color
- Black
- Warranty
- 12 months (aftermarket)
- Other Technical Attributes
- CR-Neoprene Water Pump Impeller and Seals
What’s in the Box
- 1 x Water Pump 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 negative battery cable for safety.
- Shift the outboard into the neutral gear position.
- Remove the lower unit mounting bolts and carefully lower the gearcase assembly.
- Unbolt and remove the old water pump housing, impeller, and wear plate. Note the orientation of the old parts.
- Thoroughly clean all mating surfaces, removing any old gasket material or corrosion.
- Install the new key, impeller (turn driveshaft clockwise to bend vanes correctly), wear plate, and gaskets.
- Fit the new housing over the impeller assembly and secure it with the bolts, tightening to the manufacturer's specified torque.
- Apply a light coat of marine grease to the driveshaft splines.
- Carefully reinstall the lower unit, ensuring the driveshaft, shift shaft, and water tube align correctly.
- Secure the lower unit with its mounting bolts.
- Reconnect the battery, start the engine in water, and immediately check for a steady stream from the telltale outlet.
Troubleshooting & FAQ
How do I confirm this kit fits my Mercury EFI outboard?
Check your engine's serial number. This kit is specifically for models from 2020 and newer with a serial number of 0R833820 and up. If your serial number is lower or your engine is an older model, this kit will not fit.
What are the signs of a failing water pump impeller?
Common signs include a weak or no water stream from the "telltale" outlet, engine overheating alerts or alarms, and a dry, cracked, or brittle appearance of the old impeller vanes upon inspection.
How often should the water pump impeller be replaced?
For optimal performance and to prevent engine damage, it is recommended to inspect the impeller annually and replace it every 1-2 years or every 100-200 hours of use, whichever comes first. Service intervals should be shorter in saltwater or silty conditions.
Is this kit compatible with older Mercury 4-stroke models?
No, this kit is only for the newer EFI models (2020+) with the 333cc, 2-cylinder powerhead and the corresponding cooling system design. It is not interchangeable with kits for older carbureted or different displacement models.
What is the difference between this housing and the OEM version?
This aftermarket kit features a durable marine-grade nylon housing with an SS316 stainless steel liner and wear plate. It is engineered to meet or exceed original equipment specifications for performance, corrosion resistance, and longevity.
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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