Water Pump Service Kit with Housing – Fits Mercury Mariner 9.9–20 HP 4-Stroke EFI and Tohatsu MFS15E/MFS20E
Water Pump Service Kit with Housing – Fits Mercury Mariner 9.9–20 HP 4-Stroke EFI and Tohatsu MFS15E/MFS20E is backordered and will ship as soon as it is back in stock.
Worry-free returns
Worry-free returns
Shop with confidence. If you’re not completely satisfied, eligible items may be returned within the return window, provided they are unused and in original packaging.
If the return is due to our error or a defective item, we’ll make it right.
Please contact us before returning any item.
Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
U.S. orders usually arrive within 6–15 days, depending on stock location and destination.
International delivery times may vary due to customs processing.
Tracking information will be provided once your order ships.
Water Pump Service Kit with Housing – Fits Mercury Mariner 9.9–20 H...
Water Pump Service Kit with Housing – Fits Mercury Mariner 9.9–20 HP 4-Stroke EFI and Tohatsu MFS15E/MFS20E is backordered and will ship as soon as it is back in stock.
Product Details
This Water Pump Service Kit with Housing is intended for specified Mercury Mariner 4-stroke EFI outboard models and Nissan/Tohatsu MFS15E and MFS20E outboards. It is supplied as a service kit for renewing the water pump assembly and includes the housing specified for this product.
For Mercury Mariner applications, the listed engine coverage includes 9.9 EFI models with serial numbers starting at 1R00814 and 10, 15, and 20 EFI models with serial numbers starting at 0R833820. For Nissan/Tohatsu applications, the listed fitment is MFS15E and MFS20E.
- Water pump service kit with housing.
- Designed for the specific engine families and serial-number ranges listed below.
- Use the engine model and serial number to confirm fitment before ordering.
Part Number Matrix
The following manufacturer and reference numbers are associated with this service kit in the product catalog. Reference numbers should be matched to the engine application, not used independently of the fitment information.
| Brand | Part Number | Application |
|---|---|---|
| Mercury Mariner | 8M0135821 | Mercury Mariner water pump service kit reference |
| Mercury Mariner | 98-8M0135821 | Mercury Mariner water pump service kit reference |
| Mercury Mariner | 90-8M0125267 | Catalog-listed reference |
| Mercury Mariner | 8M0137849 | Mercury Mariner water pump service kit reference |
| Mercury Mariner | 46-8M0135821 | Catalog-listed reference |
| Nissan / Tohatsu | 3RS-87322-1 | Fits listed MFS15E and MFS20E applications |
| Nissan / Tohatsu | 3RS-87322 | Fits listed MFS15E and MFS20E applications |
Engine & Model Compatibility
Confirm both the engine model and serial-number range before ordering. The conditions below must be considered together.
| Brand | Model | Rated HP | Stroke | Serial No. | Reference No. | Notes |
|---|---|---|---|---|---|---|
| Mercury Mariner | 9.9 EFI | 9.9 | 4-Stroke | 1R00814 and above | 8M0135821 / 98-8M0135821 | Catalog-listed application |
| Mercury Mariner | 10 EFI | 10 | 4-Stroke | 0R833820 and above | 8M0135821 / 98-8M0135821 | Catalog-listed application |
| Mercury Mariner | 15 EFI | 15 | 4-Stroke | 0R833820 and above | 8M0135821 / 98-8M0135821 | Catalog-listed application |
| Mercury Mariner | 20 EFI | 20 | 4-Stroke | 0R833820 and above | 8M0135821 / 98-8M0135821 | Catalog-listed application |
| Nissan / Tohatsu | MFS15E | 15 | 4-Stroke | Not specified in the catalog record | 3RS-87322-1 / 3RS-87322 | Confirm the complete model designation before ordering |
| Nissan / Tohatsu | MFS20E | 20 | 4-Stroke | Not specified in the catalog record | 3RS-87322-1 / 3RS-87322 | Confirm the complete model designation before ordering |
Technical Specs
- Product Type
- Water pump service kit with housing
- Compatible Stroke
- 4-Stroke applications listed in the compatibility table
- Installation
- Service replacement for the water pump assembly; installation should follow the engine manufacturer's service procedure
- Application
- Mercury Mariner 9.9 EFI, 10 EFI, 15 EFI, and 20 EFI models within the stated serial ranges; Nissan/Tohatsu MFS15E and MFS20E
- Housing
- Included as part of the service kit
What’s in the Box
This product is a water pump service kit supplied with a housing. The company catalog does not specify the quantity or individual contents of every internal service component, so verify the kit contents against the product image and your original assembly before installation.
- Water pump service kit
- Water pump housing
Installation Notes
- Verify the engine brand, exact model, stroke, and serial-number range against the compatibility table.
- Disconnect the battery and place the outboard in neutral before beginning service.
- Remove the lower unit according to the engine manufacturer's service procedure, taking care around the shift linkage and water tube.
- Remove the existing water pump components and inspect the driveshaft, keyway, mating surfaces, and water passages for wear, corrosion, or blockage.
- Clean the mating surfaces and install the service kit components in the correct order for the engine model.
- Ensure the impeller, housing, seals, and related parts are correctly positioned before tightening fasteners to the manufacturer's specified torque.
- Reinstall the lower unit and reconnect the shift linkage and water tube as required.
- Test the outboard using an appropriate water supply and confirm a strong tell-tale stream before returning the engine to normal operation.
Troubleshooting & FAQ
How do I confirm this kit fits my engine?
Match the complete engine information to the table. Mercury Mariner coverage is for 9.9 EFI engines starting at serial number 1R00814 and 10, 15, and 20 EFI engines starting at serial number 0R833820. Nissan/Tohatsu coverage is listed for MFS15E and MFS20E. Do not rely on horsepower alone.
What are the signs of a failing water pump?
Common warning signs include a weak or intermittent tell-tale stream, overheating, an overheating alarm, or visible damage to the impeller and housing during inspection. Stop operating an overheating engine and identify the cause before further use.
What does this service kit include?
The catalog identifies this product as a water pump service kit with housing. Because the catalog record does not list quantities for each internal component, compare the product image and the contents of the received package with the parts required for your specific engine before starting work.
Is this an OEM component?
This listing is for a replacement service kit. The reference numbers identify compatible catalog applications and are not a statement that the replacement kit is manufactured by Mercury, Mariner, Nissan, or Tohatsu.
Should a professional install the kit?
Professional installation is recommended if you are not familiar with outboard lower-unit and water-pump service. Follow the manufacturer's service information for disassembly, assembly, sealing, and torque requirements.
Safety & Important Info
- Confirm the exact model, stroke, and serial-number conditions before purchase.
- Do not operate an outboard without an adequate water supply during testing.
- Inspect all removed and replacement parts for damage, corrosion, or incorrect fit before assembly.
- Follow the engine manufacturer's service procedure and specified torque values.
- This is a replacement service kit; manufacturer names and part numbers are used only to identify applications and reference numbers.
About Sea Sierra
- Marine Application Focus — We supply replacement parts for a range of outboard maintenance and repair applications.
- Fitment Information — Product listings identify engine models, stroke types, serial ranges, and reference numbers where available.
- Service Support — Verify your engine information and the product contents before beginning installation.
Payment & Security
Payment methods
Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.
