Water Pump Impeller Service Kit for Mercury/Mariner Outboards – 4-Stroke 9.9–25 HP and 2-Stroke 20–30 HP – Replaces 47-8508910, 47-85089-3 and 47-8M0204712
Water Pump Impeller Service Kit for Mercury/Mariner Outboards – 4-Stroke 9.9–25 HP and 2-Stroke 20–30 HP – Replaces 47-8508910, 47-85089-3 and 47-8M0204712 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 Impeller Service Kit for Mercury/Mariner Outboards – 4-S...
Water Pump Impeller Service Kit for Mercury/Mariner Outboards – 4-Stroke 9.9–25 HP and 2-Stroke 20–30 HP – Replaces 47-8508910, 47-85089-3 and 47-8M0204712 is backordered and will ship as soon as it is back in stock.
Product Details
This Water Pump Impeller Service Kit is an aftermarket replacement for selected Mercury and Mariner outboard water-pump applications. Catalog-supported applications include Mercury 4-Stroke models from 9.9 HP through 25 HP and selected 2-Stroke 20, 25, and 30 HP models. Exact fitment depends on the engine model, water-pump design, gear ratio, and serial-number range.
The impeller is listed as a replacement for multiple manufacturer and aftermarket references, including Mercury 47-8508910, 47-85089-3, and 47-8M0204712, Sierra 18-3057, Mallory 9-45303, and CEF 500315. These references are provided for identification and interchange checking only; always compare the original part and verify the engine-specific conditions before ordering.
- Designed as a direct replacement for compatible water-pump impeller applications.
- Neoprene rubber impeller with a metal-alloy hub for dependable cooling-water circulation.
- Kit includes the impeller key and additional sealing components listed below.
Part Number Matrix
Use these references to compare the replacement with your original component. A part-number match does not replace engine-specific fitment verification.
| Brand | Part Number |
|---|---|
| Mercury | 47-8508910 |
| Mercury | 47-85089-3 |
| Mercury | 47-8M0204712 |
| Mercury | 47-8M0027792 |
| Mercury | 47-8M0024502 |
| Sierra | 18-3057 |
| Mallory | 9-45303 |
| CEF | 500315 |
Engine & Model Compatibility
The applications below summarize catalog-supported examples for the listed impeller reference. Serial-number, model-designation, gear-ratio, and water-pump configuration conditions must remain together when checking fitment.
| Brand | Model or Application | Rated HP | Stroke | Serial or Application Condition | Reference |
|---|---|---|---|---|---|
| Mercury | 13.5 International | 13.5 HP | 4-Stroke | Serial 0P134638 through 0P400999 | 47-8M0204712 |
| Mercury | 9.9, 323 cc | 9.9 HP | 4-Stroke | Serial 0G760300 through 1B226999 | 47-8M0204712 |
| Mercury | 9.9, 323 cc | 9.9 HP | 4-Stroke | Serial 0P075166 through 0P400999 | 47-8M0204712 |
| Mercury | 15 | 15 HP | 4-Stroke | Selected serial ranges including 0G590000 through 1B727495 | 47-8M0204712 |
| Mercury | 18 | 18 HP | Configuration varies | Selected serial ranges; verify the exact pump design | 47-8M0204712 |
| Mercury | 20, 2-cylinder | 20 HP | 2-Stroke | Selected serial ranges including 0B238464 through 0P325499 | 47-8M0204712 |
| Mercury | 25, 2-cylinder | 25 HP | 2-Stroke | Selected serial ranges including 0B238464 through 1B000001 and newer | 47-8M0204712 |
| Mercury | 25 | 25 HP | 4-Stroke | Selected serial ranges including 0G590000 through 0P388282 | 47-8M0204712 |
| Mercury | 30, 2-cylinder | 30 HP | 2-Stroke | Selected serial ranges including 0G055314 through 1B000001 and newer | 47-8M0204712 |
Important: The table is not an exhaustive fitment list. Mariner applications may use equivalent Mercury powerhead and gearcase configurations, but the exact model and serial number must be checked before installation. The previously stated Force/Chrysler and 40 HP applications are not included here because the available catalog evidence did not establish those relationships for this impeller reference.
Technical Specs
- Product Type
- Water Pump Impeller Service Kit
- Installation
- Direct replacement for compatible applications
- Material
- Neoprene rubber impeller with metal-alloy hub
- Number of Blades
- 6
- Dimensions
- Impeller height: 12.6 mm (0.50 in); overall diameter: 73.8 mm (2.91 in); hub shaft diameter: 16.0 mm (0.63 in)
- Weight
- 40 g (1.41 oz)
- Warranty
- Warranty coverage varies by seller and manufacturer; review the applicable order terms before purchase.
- Installation Requirement
- Impeller key required; a key is included in this service kit.
What’s in the Box
- 1 x Water pump impeller
- 1 x Impeller key, reference 28-85119
- 2 x Seal
- 1 x O-ring
- 1 x Gasket
Installation Notes
- Disconnect the negative battery cable before starting work.
- Remove the gearcase or lower unit according to the engine manufacturer's service procedure.
- Unbolt and remove the water-pump housing to access the impeller.
- Note the direction of the old impeller blades before removal.
- Remove the old impeller, key, gaskets, seals, and O-ring. Clean the mating surfaces thoroughly.
- Install the supplied seals, O-ring, and gasket in the correct positions for your water-pump housing.
- Install the impeller key into the driveshaft.
- Slide the new impeller onto the driveshaft while rotating it in the correct direction to seat the blades.
- Reinstall the water-pump housing and tighten fasteners to the engine manufacturer's specifications.
- Reattach the lower unit, reconnect the battery, and test the cooling-water flow in a suitable test tank or in the water.
Troubleshooting & FAQ
How do I confirm fitment for my engine?
Check the engine brand, exact model designation, horsepower, stroke, water-pump configuration, and serial number against the compatibility information. Compare the original impeller's diameter, height, hub, blade count, and keyway before installation.
What are the signs of a failing water-pump impeller?
Common symptoms include a weak or missing telltale stream, an overheating warning, irregular cooling-water flow, or visible cracks, stiffness, deformation, or missing blades on the old impeller.
How often should the impeller be replaced?
Inspect the impeller regularly and replace it when the blades become worn, stiff, cracked, permanently bent, or damaged. Replacement intervals depend on operating hours, storage conditions, and whether the engine is used in saltwater, silt, sand, or other abrasive environments.
Is everything needed for installation included?
The kit includes the impeller, key, seals, O-ring, and gasket listed in the box contents. Standard mechanic's tools and any engine-specific service materials are not included.
Is this an OEM component?
No. This is an aftermarket replacement intended for compatible applications. Mercury, Mariner, Sierra, Mallory, CEF, and other names and part numbers are used only to identify referenced applications and are not claims that this product is manufactured by those brands.
What should I do if my engine is not listed?
Do not rely on horsepower alone. Confirm the complete model and serial-number condition, compare the original component dimensions, and contact support before ordering if any detail differs.
Safety & Important Information
- Follow the engine manufacturer's service instructions and use appropriate personal protective equipment.
- Verify the original impeller, keyway, dimensions, and engine serial number before purchase.
- Do not operate an outboard with inadequate cooling-water flow or an overheating warning.
- Professional installation is recommended if you are not familiar with lower-unit and water-pump service.
- This is an aftermarket replacement, not an OEM component.
About Sea Sierra
- Pro-Grade Standards — We supply marine replacement parts selected for dependable service in real-world operating conditions.
- Fast Global Fulfillment — Standard delivery options and estimated transit times are shown at checkout based on the destination.
- Manufacturer-Direct Value — Practical replacement parts at competitive pricing without unnecessary markup.
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.
