Water Pump Impeller Kit – Fits Yamaha & Mariner 20-30 HP (Replaces 689-W0078-A6/A4, 18-3426/3427)
Water Pump Impeller Kit – Fits Yamaha & Mariner 20-30 HP (Replaces 689-W0078-A6/A4, 18-3426/3427) is backordered and will ship as soon as it is back in stock.
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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.
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Water Pump Impeller Kit – Fits Yamaha & Mariner 20-30 HP (Repla...
Water Pump Impeller Kit – Fits Yamaha & Mariner 20-30 HP (Replaces 689-W0078-A6/A4, 18-3426/3427) is backordered and will ship as soon as it is back in stock.
Product Details
This Water Pump Impeller Kit – Fits Yamaha 20/25/30 HP Outboards & Mariner 20/25/30 HP (Replaces 689-W0078-A6/689-W0078-A4) is designed to restore cooling system performance on a range of two-stroke outboards. It is engineered for Yamaha 25 HP and 30 HP models from 1984 through 1997 (including C25, CV25, C30, and CV30) and specific Mariner 20 HP, 25 HP, and 30 HP models including the 20C, 25C, and 30A which require serial number verification.
This comprehensive kit serves as a direct replacement for Yamaha part numbers 689-W0078-A6-00, 689-W0078-A4-00, and 689-W0078-04-00. It also cross-references with Sierra Marine 18-3426/18-3427, GLM Marine 12059/12058, and Mariner 42431M/84829M/97793M/97793T.
- Includes all necessary gaskets, seals, and hardware for a complete overhaul.
- Engineered for direct OEM-level fit and easy installation.
- Designed for improved durability and higher flow rates for optimal engine cooling.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket brands.
| Brand | Part Number |
|---|---|
| Yamaha | 689-W0078-A6-00 |
| Yamaha | 689-W0078-A4-00 |
| Yamaha | 689-W0078-04-00 |
| Sierra Marine | 18-3426 |
| Sierra Marine | 18-3427 |
| GLM Marine | 12059 |
| GLM Marine | 12058 |
| Mariner | 42431M |
| Mariner | 84829M |
| Mariner | 97793M |
| Mariner | 97793T |
Engine & Model Compatibility
Confirm your engine model and year in the table below.
For Yamaha Owners: This kit fits select 2-stroke 25 HP and 30 HP models manufactured between 1984 and 1997. Please verify your specific model (e.g., C25, CV30) and year carefully.
For Mariner Owners: Fitment for models 20C, 25C, and 30A is dependent on the serial number prefix. Please verify your engine's serial number starts with 6A9 or 684 as indicated in the notes column.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | 25 HP | 25 | 2-Stroke | 1984–1985 | 689-W0078-A6-00 | |
| Yamaha | 25 HP | 25 | 2-Stroke | 1986–1987 | 689-W0078-A6-00 | |
| Yamaha | C25 | 25 | 2-Stroke | 1991–1997 | 689-W0078-A6-00 | |
| Yamaha | CV25 | 25 | 2-Stroke | 1990 | 689-W0078-A6-00 | |
| Yamaha | 30 HP | 30 | 2-Stroke | 1986 | 689-W0078-A6-00 | |
| Yamaha | C30 | 30 | 2-Stroke | 1991–1992 | 689-W0078-A6-00 | |
| Yamaha | CV30 | 30 | 2-Stroke | 1989–1990 | 689-W0078-A6-00 | |
| Mariner | 20C | 20 | 2-Stroke | All Years | 42431M | S/N prefix number 6A9 |
| Mariner | 25C | 25 | 2-Stroke | All Years | 42431M | S/N prefix number 6A9 |
| Mariner | 30A | 30 | 2-Stroke | All Years | 42431M | S/N prefix number 684 |
Technical Specs
- Product Type
- Water Pump Impeller Repair Kit
- Installation
- Direct OEM Replacement
- Other Technical Attributes
- Designed for durability with higher flow rates for optimal engine cooling
What’s in the Box
- 1 x Water Pump Impeller (689-44352-02-00)
- 1 x Woodruff Key (664-44338-00-00)
- 1 x Pump Housing (689-44311-03-00)
- 1 x Insert Cartridge (689-W4432-01-00)
- 1 x Wear Plate (689-44323-02-00)
- 1 x Gasket (689-44324-A0-00)
- 1 x Gasket (689-44315-A0-00)
- 1 x Water Seal (626-44365-01-00)
- 3 x Bolt with washer (97080-06030-00)
Installation Notes
- Disconnect the battery and shift the outboard into neutral.
- Unbolt and remove the lower unit (gearcase) from the outboard's driveshaft housing. You may need to disconnect the shift linkage.
- Locate and unbolt the water pump housing, typically found on top of the gearcase.
- Carefully remove the old impeller, housing, wear plate, gaskets, and seals. Note the orientation of the impeller vanes.
- Clean all mating surfaces thoroughly, removing any old gasket material or corrosion.
- Install the new components from the kit in the reverse order of removal. Lightly grease the new impeller and insert it while turning the driveshaft clockwise to seat the vanes correctly.
- Ensure all gaskets are properly aligned and torque the housing bolts to the manufacturer's specification.
- Reinstall the lower unit, connect the shift linkage, and test the engine in the water, confirming a steady stream from the tell-tale outlet.
Troubleshooting & FAQ
How do I confirm this kit fits my engine?
Check your engine's model, horsepower, and year against the compatibility table. For Mariner models, you must also verify your engine's serial number prefix matches the one listed in the notes.
What are the signs of a failing water pump impeller?
Common symptoms include the engine overheating at idle or low speeds, a weak or non-existent water stream from the "tell-tale" outlet, and in some cases, a faint burning rubber smell from the exhaust.
How often should I replace my outboard's impeller?
As a best practice for preventative maintenance, it is recommended to replace the impeller every 1-2 years or every 100-200 hours of use, whichever comes first, even if no issues are apparent. Refer to your engine's service manual for specific intervals.
What's the difference between the Yamaha -A6, -A4, and -04 kits?
These are superseded part numbers from Yamaha. The -A6 part is the most recent OEM version, but this aftermarket kit is designed to replace all of them, providing the same fit and function.
My Mariner model is listed as "All Years". How do I confirm fitment?
For the Mariner 20C, 25C, and 30A models, compatibility depends on the manufacturing run, which is identified by the serial number (S/N) prefix. You must ensure your engine's S/N prefix is either '6A9' or '684' as specified in our compatibility table.
Is this an OEM part or an aftermarket equivalent?
This listing is for a high-quality aftermarket replacement part, not an OEM component. It has been manufactured in an ISO 9002 certified facility to meet or exceed OEM specifications for material and performance, and is batch-inspected for consistency.
How fast will my order ship?
We ship worldwide, with most orders arriving within 5–15 business days. We offer free standard shipping, and expedited options are available at checkout for most destinations.
What is the warranty and return policy?
This Water Pump Kit is covered by a 1-year warranty against manufacturing defects under normal marine use. If you encounter a problem, please contact our support team with your order number. Unused parts in their original condition can be returned within our standard return window; check our policy page or contact us for details.
Safety & Important Info
- Verify images and specifications against your original part before purchase. 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 quality control.
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