Water Pump Impeller Service Kit – Fits Mercury/Mariner 13.5-25 HP Outboards (Replaces 47-8508910, 47-850893, 47-8M0027792)
Water Pump Impeller Service Kit – Fits Mercury/Mariner 13.5-25 HP Outboards (Replaces 47-8508910, 47-850893, 47-8M0027792) 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.
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Water Pump Impeller Service Kit – Fits Mercury/Mariner 13.5-25 HP O...
Water Pump Impeller Service Kit – Fits Mercury/Mariner 13.5-25 HP Outboards (Replaces 47-8508910, 47-850893, 47-8M0027792) 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 designed for a wide range of Mercury and Mariner outboards, including 4-Stroke 13.5, 15, 18, and 25 HP models (1984–2005) as well as 2-Stroke 20-40 HP models (1996–1999). It is engineered to restore cooling system performance and prevent engine overheating.
The kit directly replaces multiple OEM and aftermarket part numbers, including Mercury 47-8508910, 47-850893, 47-8M0027792, 47-8M0024502, Sierra 18-3057, and Mallory 9-45303, ensuring broad interchange compatibility.
- Installs as a direct OEM-equivalent replacement.
- Features a durable, high-performance neoprene rubber impeller for reliable water flow.
- The kit includes the esssential impeller key required for installation.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 47-8508910 |
| Mercury | 47-850893 |
| Mercury | 47-8M0027792 |
| Mercury | 47-8M0024502 |
| Mercury | 47-8M0204712 |
| Sierra | 18-3057 |
| Mallory | 9-45303 |
| CEF | 500315 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Force/Chrysler models, please verify your serial number against the ranges listed in the notes to ensure correct fitment.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | 4-Stroke | 13.5 HP | 4-Stroke | 1984–2005 | 47-8508910 | Current part 47-8M0204712 |
| Mercury | 4-Stroke | 15 HP | 4-Stroke | 1984–2005 | 47-8508910 | Current part 47-8M0204712 |
| Mercury | 4-Stroke | 18 HP | 4-Stroke | 1984–2005 | 47-8508910 | Current part 47-8M0204712 |
| Mercury | 4-Stroke | 25 HP | 4-Stroke | 1984–2005 | 47-8508910 | Current part 47-8M0204712 |
| Mercury | 2-Cylinder | 20 HP | 2-Stroke | 1996–1999 | 47-8508910 | Current part 47-8M0204712 |
| Mercury | 2-Cylinder | 25 HP | 2-Stroke | 1996–1999 | 47-8508910 | Current part 47-8M0204712 |
| Mercury | 2-Cylinder | 30 HP | 2-Stroke | 1996–1999 | 47-8508910 | Current part 47-8M0204712 |
| Mercury | 2-Cylinder | 40 HP | 2-Stroke | 1996–1999 | 47-8508910 | Current part 47-8M0204712 |
| Mercury | 4-Stroke (323cc) | 9.9 HP | 4-Stroke | 1996–2005 | 47-8508910 | Current part 47-8M0204712 |
| Force/Chrysler | Force | 25 HP | 2-Stroke | 1996–1998 | 47-8508910 | Serial# E127700-E344999 |
| Force/Chrysler | Force | 40 HP | 2-Stroke | 1995–1999 | 47-8508910 | Serial# E093700-E369299 |
| Force/Chrysler | Force | 50 HP | 2-Stroke | 1995–1999 | 47-8508910 | Serial# E093700-E369299 |
| Force/Chrysler | Force | 75 HP | 2-Stroke | 1999 | 47-8508910 | Serial# E345000-Up |
Technical Specs
- Product Type
- Water Pump Impeller Service Kit
- Installation
- Direct OEM replacement
- Material
- Neoprene rubber impeller with metal alloy hub
- Number of Blades
- 6
- Dimensions
- Impeller Height: 12.6 mm (0.50 inches), Overall Diameter: 73.8 mm (2.91 inches), Hub Shaft Diameter: 16.0 mm (0.63 inches)
- Weight
- 40 g (1.41 oz)
- Warranty
- Varies by manufacturer (typically 1 year)
- Other Technical Attributes
- Requires impeller key for installation (typically included in kit)
What’s in the Box
- 1 x Water Pump Impeller (47-8508910)
- 1 x Impeller Key (28-85119)
- 2 x Seal
- 1 x O-Ring
- 1 x Gasket
Installation Notes
- Disconnect the negative battery cable before starting.
- Remove the gearcase/lower unit from the outboard motor.
- Unbolt and remove the water pump housing to access the impeller.
- Take note of the old impeller's blade direction before removing it.
- Remove the old impeller, key, gaskets, and seals. Clean all mating surfaces thoroughly.
- Install the new O-ring, seals, and gaskets as provided in the kit.
- Install the new impeller key into the driveshaft.
- Slide the new impeller onto the driveshaft, rotating it in the correct direction to seat the blades.
- Reinstall the water pump housing, ensuring a proper seal.
- Reattach the lower unit to the outboard, reconnect the battery, and test operation in water.
Troubleshooting & FAQ
How do I know if this impeller kit fits my specific engine?
The best way to confirm fitment is to check your engine's model, horsepower, and year against the compatibility table provided. For Force/Chrysler models, you must also verify your engine's serial number falls within the specified range.
What are the signs of a failing water pump impeller?
Common symptoms include a weak or non-existent "telltale" water stream, engine overheating alarms, and reduced engine performance. Visible signs on the old impeller include cracked, stiff, or missing blades.
How often should I replace the impeller?
As a general maintenance guideline, impellers should be inspected annually and replaced every 1-2 years or every 100-200 hours of use, depending on operating conditions (e.g., saltwater vs. freshwater).
Is everything needed for installation included?
This kit includes the impeller, key, seals, O-ring, and gasket. You will need standard mechanic's tools and potentially a sealant, which are not included.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. 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 QC.
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