Water Pump Impeller Repair Kit – Fits Mercury/Mariner 15 HP Outboards (Replaces 8M0070780, 42038Q3)
Water Pump Impeller Repair Kit – Fits Mercury/Mariner 15 HP Outboards (Replaces 8M0070780, 42038Q3) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
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Water Pump Impeller Repair Kit – Fits Mercury/Mariner 15 HP Outboar...
Water Pump Impeller Repair Kit – Fits Mercury/Mariner 15 HP Outboards (Replaces 8M0070780, 42038Q3) is backordered and will ship as soon as it is back in stock.
Product Details
This Water Pump Impeller Repair Kit is engineered for Mercury and Mariner 15 HP two-stroke outboard motors. It includes all the essential components to service the lower unit water pump assembly, addressing a worn or damaged impeller to restore engine cooling performance.
This kit is a direct replacement for Mercury part numbers 8M0070780, 42038T3, and Quicksilver aftermarket number 42038Q3.
- Installation Location: Lower unit gearcase.
- Specific Fitment: Designed for Mercury/Mariner 15 HP carburetor models with SeaPro designation.
- Function: Restores water circulation to prevent engine overheating.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Notes |
|---|---|---|
| Mercury | 8M0070780 | OEM Part Number |
| Mercury | 42038T3 | Alternative OEM Number |
| Quicksilver | 42038Q3 | Aftermarket Replacement |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Mercury & Mariner Outboards: This kit is intended for the specific 2-stroke models listed. Always verify your engine's serial number or original part number before ordering.
| Brand | Model | Rated HP | Stroke | OEM Part No. | Notes |
|---|---|---|---|---|---|
| Mercury | 15 HP Carb SeaPro | 15 | 2-Stroke | 8M0070780 | Lower unit gearcase |
| Mercury | 15 HP | 15 | 2-Stroke | 42038T3 | For Mercury and Mariner outboards |
| Mercury/Mariner | 6–15 HP | 6–15 | 2-Stroke | 42038Q3 | Quicksilver aftermarket part |
Technical Specs
- Product Type
- Water Pump Impeller Repair Kit
- Installation
- Lower unit replacement
- Housing Color
- Black
- Compatible Engines
- Fits Mercury/Mariner 15 HP carburetor models with SeaPro designation
What’s in the Box
- Water Pump Impeller (Replaces 42038K02)
- Gaskets and Seals
- Housing Components
Installation Notes
- Disconnect the battery and shift linkage.
- Remove the lower unit mounting bolts and carefully lower the gearcase assembly.
- Unbolt and remove the existing water pump housing.
- Note the rotational direction of the old impeller's vanes before removal.
- Clean all mating surfaces of debris and old gasket material.
- Install the new wear plate, gaskets, and seals as provided in the kit.
- Slide the new impeller onto the driveshaft, turning the shaft clockwise to seat the vanes correctly inside the housing.
- Reinstall the water pump housing and torque its bolts to manufacturer specifications.
- Carefully guide the lower unit back into place, ensuring the driveshaft and water tube align.
- Secure the mounting bolts, reattach the shift linkage, and reconnect the battery.
- Start the engine and immediately check the tell-tale for a strong, steady stream of water.
Troubleshooting & FAQ
How do I know if my water pump impeller is failing?
Common signs of a failing impeller include a weak or non-existent water stream from the "tell-tale" outlet, engine overheating alarms, or a reduction in engine performance. Visible damage like cracked, brittle, or missing vanes on the old impeller during an inspection also indicates a need for replacement.
How often should this part be replaced?
As a routine maintenance item, it is recommended to replace the water pump impeller every 1 to 2 years or every 100-200 hours of operation, whichever comes first. Service intervals should be shorter for boats used in saltwater or in water with heavy sediment.
Will this kit fit 4-stroke Mercury models?
No, this kit is specifically designed for the 15 HP 2-stroke outboard models listed in the compatibility table, including SeaPro variants. It is not compatible with 4-stroke engines. Always confirm your engine's specific model and part number requirements before ordering.
What is the difference between the part numbers 8M0070780, 42038T3, and 42038Q3?
These part numbers are interchangeable for this application. 8M0070780 is a primary Mercury OEM part number, 42038T3 is a related OEM number, and 42038Q3 is a common cross-reference for the Quicksilver aftermarket equivalent. All are designed to fit the same set of engines.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). It is built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, it is batch-inspected for consistency and quality.
Shipping speed & cost
We ship worldwide quickly—typical transit is 5–15 days. Standard shipping is free; expedited options will appear at checkout where available.
Warranty & returns
This product is covered by a 1-year warranty against manufacturing defects under normal use. If any issues arise, please contact our support team with your order details. Returns are accepted within our standard window for items that are unused and in their original condition. See our full policy page or reach out for instructions.
Safety & Important Info
- Verify the images and specifications against your original part before purchasing. If anything differs—even if your model appears on a compatibility list—do not purchase.
- This is an aftermarket replacement part, not an original equipment manufacturer (OEM) component.
- Professional installation is highly recommended for safety, proper function, and optimal performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and rigorously tested for real-world conditions.
- Fast Global Fulfillment — We offer free standard delivery to most regions, with an average transit time of 5–15 days.
- Manufacturer-Direct Value — Our model provides fair pricing without compromising on materials or quality control.
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