Water Pump Impeller Repair Kit for Mercury/Mariner 15 HP 2-Stroke Outboards – Replaces 8M0070780, 42038T3 and 42038Q3
Water Pump Impeller Repair Kit for Mercury/Mariner 15 HP 2-Stroke Outboards – Replaces 8M0070780, 42038T3 and 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 for Mercury/Mariner 15 HP 2-Stroke O...
Water Pump Impeller Repair Kit for Mercury/Mariner 15 HP 2-Stroke Outboards – Replaces 8M0070780, 42038T3 and 42038Q3 is backordered and will ship as soon as it is back in stock.
Product Details
This Water Pump Impeller Repair Kit is designed for Mercury and Mariner 15 HP two-stroke outboard motors. It provides the essential components needed to service the lower-unit water pump assembly and replace a worn or damaged impeller, helping restore proper cooling-water circulation.
The kit is listed as a replacement for Mercury part numbers 8M0070780 and 42038T3, with 42038Q3 identified as a related Quicksilver replacement reference. Confirm your engine model, serial number, and original part number before ordering.
- Installation Location: Lower-unit gearcase water pump.
- Primary Fitment: Mercury and Mariner 15 HP carburetor two-stroke models, including applicable SeaPro variants.
- Function: Replaces the water-pump impeller and service components to help maintain water circulation and reduce the risk of overheating.
Part Number Matrix
Use the references below to compare the listed OEM and aftermarket numbers with the part removed from your outboard.
| Brand | Part Number | Reference Type |
|---|---|---|
| Mercury | 8M0070780 | OEM reference |
| Mercury | 42038T3 | Related OEM reference |
| Quicksilver | 42038Q3 | Aftermarket replacement reference |
Engine & Model Compatibility
Compatibility depends on the exact model, year, serial-number range, and water-pump configuration. Verify the original part number and compare the supplied components before installation.
For Mercury and Mariner Outboards: This listing is intended for the applicable 2-stroke models shown below. It is not presented as a universal fit for every engine within the stated horsepower range.
| Brand | Model Description | Rated HP | Stroke | Reference Part No. | Installation Area |
|---|---|---|---|---|---|
| Mercury | 15 HP carburetor SeaPro models | 15 | 2-Stroke | 8M0070780 | Lower-unit gearcase |
| Mercury | Applicable 15 HP outboard models | 15 | 2-Stroke | 42038T3 | Lower-unit water pump |
| Mercury/Mariner | Applicable models using the 42038Q3 reference | 6–15 | 2-Stroke | 42038Q3 | Quicksilver replacement reference; verify exact fitment |
Technical Specs
- Product Type
- Water pump impeller repair kit
- Installation Area
- Lower-unit water pump assembly
- Housing Color
- Black
- Compatible Engines
- Applicable Mercury and Mariner 15 HP carburetor two-stroke models, including applicable SeaPro variants
- Replacement References
- 8M0070780, 42038T3, and 42038Q3
What’s in the Box
- Water pump impeller, replacing the listed 42038K02 reference
- Gaskets and seals
- Water-pump housing components
Installation Notes
- Disconnect the battery and place the outboard in a secure service position.
- Disconnect the shift linkage as required, then remove the lower-unit mounting bolts and carefully lower the gearcase.
- Remove the existing water-pump housing and inspect the pump cavity, wear plate, driveshaft, and water tube.
- Note the rotational direction of the old impeller vanes before removing the impeller.
- Clean all mating surfaces and remove debris or old gasket material.
- Install the supplied wear plate, gaskets, seals, and other pump components in the correct sequence.
- Install the new impeller on the driveshaft, turning the shaft in the correct direction so the vanes seat properly inside the housing.
- Reinstall the water-pump housing and tighten its fasteners to the outboard manufacturer’s specifications.
- Carefully reinstall the lower unit, ensuring that the driveshaft, water tube, and shift linkage align correctly.
- Secure the mounting bolts, reconnect the shift linkage, and reconnect the battery.
- Run the engine according to safe operating procedures and check for a strong, steady tell-tale stream and signs of leakage or overheating.
Troubleshooting & FAQ
How do I know if the water-pump impeller is failing?
Common signs include a weak or absent tell-tale stream, an overheating warning, or reduced engine performance. During inspection, cracked, brittle, distorted, or missing impeller vanes also indicate that replacement is needed.
How often should the impeller be replaced?
The impeller is a routine maintenance item. A commonly used service interval is every 1–2 years or 100–200 operating hours, whichever comes first, although the correct interval depends on the engine manufacturer’s schedule and operating conditions. Saltwater, sediment, and extended storage may require more frequent service.
Will this kit fit 4-stroke Mercury models?
No. This listing is intended for the applicable 2-stroke Mercury and Mariner models described above, including applicable 15 HP SeaPro variants. Do not use it on a 4-stroke engine unless the exact original part number confirms compatibility.
What is the difference between 8M0070780, 42038T3, and 42038Q3?
These are listed reference numbers associated with the application. 8M0070780 and 42038T3 are Mercury references, while 42038Q3 is identified as a Quicksilver replacement reference. Reference numbers should be compared with the original part and exact engine model before ordering; their appearance in the same listing does not replace model and serial-number verification.
Is this an OEM part?
This listing is for an aftermarket replacement kit, not a genuine Mercury OEM component. It is intended to replace the listed references for the applicable application.
What are the shipping terms?
Worldwide shipping is available. Typical transit is 5–15 days, and standard shipping is free where offered. Expedited options, availability, and final delivery estimates are shown at checkout.
What are the warranty and return terms?
The product is covered by a 1-year warranty against manufacturing defects under normal use. Returns are accepted within the standard return period for unused items in their original condition. Contact customer support with your order details for assistance.
Safety & Important Information
- Verify the engine model, year, serial number, original part number, and component appearance before purchasing.
- Do not rely on horsepower alone to determine fitment. If the original part or pump configuration differs, do not install the kit.
- This is an aftermarket replacement part, not a genuine original-equipment Mercury component.
- Follow the outboard manufacturer’s service procedures and torque specifications. Professional installation is recommended when the correct procedure is not familiar.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts designed for dependable service in real-world boating conditions.
- Fast Global Fulfillment — Free standard delivery is offered to most regions, with typical transit times of 5–15 days.
- Manufacturer-Direct Value — Our model provides practical marine replacement parts at competitive prices.
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