Water Pump Impeller – Fits Mercury/Tohatsu 8-20 HP 4-Stroke Outboards (Replaces 47-803748)
Water Pump Impeller – Fits Mercury/Tohatsu 8-20 HP 4-Stroke Outboards (Replaces 47-803748) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
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Water Pump Impeller – Fits Mercury/Tohatsu 8-20 HP 4-Stroke Outboar...
Water Pump Impeller – Fits Mercury/Tohatsu 8-20 HP 4-Stroke Outboards (Replaces 47-803748) is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket Water Pump Impeller – Fits Mercury/Tohatsu 8-20 HP 4-Stroke Outboards is engineered for a wide range of applications, including Mercury/Tohatsu 8–20 HP 4-Stroke (2003 and newer), Command Thrust models, 209cc Mercury engines, and select Honda 7.5–10 HP 4-Stroke outboards.
It provides a direct interchange for numerous OEM and aftermarket part numbers from leading brands like Mercury, Tohatsu, Honda, and more.
- Installs directly using the included key and existing keyway.
- Constructed from high-durability neoprene rubber with a hardened nylon insert for longevity.
- Kit includes one impeller and one impeller key for a complete replacement.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 47-803748 |
| Mercury | 8M0135803 |
| Mercury | 8M0214944 |
| Tohatsu | 334-65021-0 |
| Tohatsu | 334650210M |
| Honda | 19210-935-003 |
| Evinrude/Johnson | 5040046 |
| Sierra | 18-8921 |
| CEF Marine | 500383 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
Provides coverage for many Mercury/Mariner 4-stroke models from 8 to 20 HP, including Command Thrust and international variants.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | 8 HP Command Thrust | 8 | 4-Stroke | 2003+ | 47-803748 | 209cc models |
| Mercury | 9.9 HP Command Thrust | 9.9 | 4-Stroke | 2003+ | 47-803748 | 209cc models |
| Mercury | 9.9 HP International | 9.9 | 4-Stroke | 47-803748 | 2 cylinder models | |
| Mercury | 10 HP | 10 | 4-Stroke | 47-803748 | ||
| Mercury | 15 HP | 15 | 4-Stroke | 2003+ | 47-803748 | |
| Mercury | 15 HP Super International | 15 | 4-Stroke | 47-803748 | ||
| Mercury | 18 HP | 18 | 4-Stroke | 47-803748 | ||
| Mercury | 20 HP | 20 | 4-Stroke | 47-803748 |
Fits a wide range of Tohatsu and Nissan 2-stroke and 4-stroke outboards from 9.9 to 20 HP.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Tohatsu | M9.9, NS9.9 | 9.9 | 2-Stroke | 334-65021-0 | ||
| Tohatsu | M15, NS15 | 15 | 2-Stroke | 334-65021-0 | ||
| Tohatsu | M18, NS18 | 18 | 2-Stroke | 334-65021-0 | ||
| Tohatsu | MFS9.9, NSF9.9C | 9.9 | 4-Stroke | 334-65021-0 | ||
| Tohatsu | MFS15, NSF15 | 15 | 4-Stroke | 334-65021-0 | ||
| Tohatsu | MFS18, NSF18 | 18 | 4-Stroke | 334-65021-0 | ||
| Tohatsu | MFS20, NSF20 | 20 | 4-Stroke | 334-65021-0 |
Applicable to some Honda 4-stroke models, primarily in the 7.5 to 10 HP range.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Honda | BF75, BF75Z, BF75K1-K3 | 7.5 | 4-Stroke | 19210-935-003 | ||
| Honda | BF100, BF100Z | 10 | 4-Stroke | 19210-935-003 | ||
| Honda | BF75Z | 75 | 4-Stroke | 19210-935-003 | Less common application | |
| Honda | BF100Z | 100 | 4-Stroke | 19210-935-003 | Less common application |
Listed as compatible with select Evinrude/Johnson 15 HP applications.
| Brand | Model | Rated HP | OEM Part No. | Notes |
|---|---|---|---|---|
| Evinrude | Various | 15 | 5040046 |
Technical Specs
- Product Type
- Water Pump Impeller
- Material
- Neoprene rubber with hardened nylon insert
- Number of Blades
- 8
- Height
- 23.8 mm (0.94 in)
- Diameter
- 41.2 mm (1.62 in)
- Hub Diameter
- 14.0 mm (0.55 in)
- Weight
- 0.70 oz (19.8 g)
- Color
- Black
- Installation Type
- Keyway
- Warranty
- 1 Year (aftermarket)
What’s in the Box
- 1 x Water Pump Impeller (47-803748)
- 1 x Impeller Key (28-803749)
Installation Notes
- Disconnect the battery and remove the engine cover.
- Place the outboard in neutral and drain the lower unit gear oil.
- Remove the bolts securing the lower unit to the engine.
- Carefully separate the lower unit, taking note of the shift shaft linkage.
- Unbolt and remove the water pump housing cover.
- Slide the old impeller off the driveshaft, removing the old key.
- Clean the housing and base plate, inspecting for wear or damage.
- Insert the new impeller key into the driveshaft keyway.
- Align the new impeller with the key and slide it onto the shaft.
- Reinstall the housing, ensuring the blades are oriented correctly (turn the shaft clockwise).
- Reassemble the lower unit in the reverse order of removal.
- Refill the gear oil and test the engine with a water supply.
Troubleshooting & FAQ
How do I confirm this impeller fits my specific engine model?
The best way is to cross-reference your existing part number with our Part Number Matrix. Additionally, check our Engine & Model Compatibility tables. If your model or part number is not listed, this part may not fit.
What are common signs of a worn or failed impeller?
A weak or no water stream from the "tell-tale" port, engine overheating alarms, or a noticeable decrease in engine cooling performance are all indicators that the impeller may need inspection or replacement.
How often should a water pump impeller be replaced?
As a preventative maintenance item, it is recommended to replace the impeller every 1-2 years or every 100-200 hours of operation, whichever comes first. This interval can be shorter in saltwater or silty/sandy conditions.
Why is the included impeller key important?
The key is a small but critical component that locks the impeller to the driveshaft, ensuring it spins correctly to pump water. Always use a new key during installation, as the old one may be worn or fatigued.
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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