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)

This water pump impeller repair kit is designed for Mercury and Mariner 15 HP two-stroke outboard motors. It provides all the necessary components to replace a worn or damaged impeller in the lower unit water pump assembly, restoring cooling system performance and preventing engine overheating.

This kit is a direct replacement for Mercury part numbers 8M0070780 and 42038T3, as well as Quicksilver aftermarket part number 42038Q3.

• Fits specific Mercury/Mariner 15 HP carburetor models with the SeaPro designation.
• Engineered for lower unit water pump assembly installation.
• Provides a cost-effective solution for routine lower unit maintenance.

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below. For Mercury owners, here’s a guide to help you identify your engine’s serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

Technical Specifications

Installation Guide

1. Safety First: Disconnect the spark plug leads and the battery to prevent accidental starting.
2. Access Lower Unit: Place the outboard in neutral. Remove the bolts securing the lower unit (gearcase) to the upper leg.
3. Remove Gearcase: Carefully lower the gearcase away from the engine. The driveshaft will slide out from the powerhead.
4. Disassemble Pump: Locate the water pump housing on top of the gearcase. Unbolt and remove the housing to expose the impeller.
5. Inspect and Clean: Note the rotational direction of the old impeller's vanes before removing it. Clean all gasket surfaces and inspect the housing and wear plate for scoring or warping.
6. Install New Impeller: Install the new gaskets and wear plate. Slide the new impeller onto the driveshaft, ensuring its vanes are oriented in the same direction as the old one.
7. Reassemble Pump: Lightly lubricate the inside of the pump housing and install it over the new impeller, using a twisting motion to bed the vanes correctly. Securely tighten the housing bolts.
8. Reinstall Lower Unit: Carefully guide the driveshaft and water tube back into position while raising the lower unit. Bolt the gearcase back onto the engine leg.
9. Final Checks: Reconnect the spark plug leads and battery. Operate the engine using a flush-muzzle or in the water, and confirm a steady stream of water is exiting the tell-tale port.

Troubleshooting & FAQ

How do I know if this kit fits my Mercury 15 HP?
This kit is specifically for 15 HP two-stroke models, including the Carb SeaPro versions. The best way to confirm fitment is to check the "Compatible Engine Models" table and cross-reference your engine's original part number with 8M0070780, 42038T3, or 42038Q3.

What are the signs of a failing water pump impeller?
Common signs include a weak or intermittent water stream from the "telltale" outlet, engine overheating alerts or alarms, or a noticeable decrease in cooling performance, especially at low speeds.

How often should I replace the water pump impeller?
For preventative maintenance, it is recommended to inspect and/or replace the impeller every 1-2 years or every 100-200 hours of use. Frequency may depend on operating conditions (e.g., saltwater use may require more frequent changes).

OEM vs. Aftermarket?
This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

How fast do you ship and how much does it cost?
We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

What is your warranty and return policy?
This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.