Water Pump Impeller – Fits Mercury/Tohatsu/Nissan 8/9.9HP 4-Stroke, 6/8/9.8HP 2-Stroke (Replaces 47-8037481, 3B2-65021-1)
Water Pump Impeller – Fits Mercury/Tohatsu/Nissan 8/9.9HP 4-Stroke, 6/8/9.8HP 2-Stroke (Replaces 47-8037481, 3B2-65021-1) is backordered and will ship as soon as it is back in stock.
Couldn't load pickup availability
Worry-free returns
Worry-free returns
You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).
If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.
Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Water Pump Impeller – Fits Mercury/Tohatsu/Nissan 8/9.9HP 4-Stroke,...
Product Details
This Water Pump Impeller – Fits Mercury/Tohatsu/Nissan 8/9.9HP 4-Stroke, 6/8/9.8HP 2-Stroke (Replaces 47-8037481, 3B2-65021-1) is an essential replacement component for maintaining your engine’s cooling system. It is designed for a precise fit on Mercury 8/9.9HP 4-Stroke (2005 and newer) and 6/8/9.8HP 2-Stroke international models. It also covers a wide range of Tohatsu/Nissan 6/8/9.8HP 2-Stroke and 8/9.8HP 4-Stroke outboards, as well as Parsun F6, F8, and F9.8 models.
It serves as a direct interchange for several part numbers, including Mercury 47-8037481, Tohatsu 3B2-65021-1, Sierra 18-3086, CEF 500344, and Mallory 9-45210.
- Installs in the lower unit's water pump assembly.
- Made from durable neoprene rubber for reliable performance.
- Includes the required square key for driveshaft mounting.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 47-8037481 |
| Mercury | 8037481 |
| Mercury | 8M0214945 |
| Tohatsu | 3B2-65021-1 |
| Tohatsu | 3B2650211 |
| Sierra | 18-3086 |
| CEF | 500344 |
| Mallory | 9-45210 |
| Parsun (Aftermarket) | PAF8-04000200 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Mercury models, this impeller fits a range of 2-cylinder international engines and non-BigFoot 4-stroke models from 2005 onwards. Ensure your serial number is 0P325500 or higher for the 8/9.9HP 4-stroke engines.
For Tohatsu and Nissan, this part is used across 2-stroke and 4-stroke platforms. Compatibility for Nissan relies on models that share the same design as their Tohatsu counterparts.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | 8/9.9 (209cc) | 8/9.9 | 4-Stroke | 2005+ (0P325500+) | 47-8037481 | Non-BigFoot models |
| Mercury | 8/9.9 HP | 8/9.9 | 4-Stroke | 2005+ | 47-8037481 | Various models |
| Mercury | 8/9.8 SeaPro | 8/9.8 | 2-Stroke | Various | 47-8037481 | 2 cylinder (International) models |
| Mercury | 6/8 | 6/8 | 2-Stroke | Various | 47-8037481 | 2 cylinder (International) models |
| Tohatsu | Various | 6/8/9.8 | 2-Stroke | Various | 3B2-65021-1 | All compatible models |
| Tohatsu | MFS8/MFS9.8 | 8/9.8 | 4-Stroke | Various | 3B2-65021-1 | All compatible models |
| Nissan | Various | 6/8/9.8 | 2-Stroke | Various | 3B2-65021-1 | Models sharing same design with Tohatsu |
| Parsun | F6/F8/F9.8 | 6/8/9.8 | Not Specified | Various | Compatible | Aftermarket fit |
Technical Specs
- Product Type
- Water Pump Impeller
- Installation
- Replaceable component in lower unit water pump assembly
- Outer Diameter
- 40.00mm
- Inner Shaft Diameter
- 11.58mm
- Hub Height
- 17.76mm
- Material
- Neoprene rubber
- Number of Blades
- 6
- Hub Type
- Plastic
- Rotation
- Clockwise
- Key Type
- Square key required for installation
- Operating Temperature
- -10°C to 80°C (14°F to 176°F)
- Warranty
- Varies by seller (typically 1 year warranty against manufacturing defects)
What’s in the Box
- 1 x Water Pump Impeller (47-8037481/3B2-65021-1)
- 1 x Square Key (for driveshaft mounting)
Installation Notes
- Disconnect the spark plug wires and shift the engine into neutral.
- Place a drain pan under the gearcase and remove the drain screw to empty the gear oil.
- Remove the bolts securing the lower unit (gearcase) to the upper leg assembly.
- Carefully lower the gearcase to expose the driveshaft and water pump housing.
- Unscrew the bolts on the water pump housing and lift it to access the impeller.
- Remove the old impeller, noting its blade orientation. Slide off the old key if present.
- Clean the housing interior and inspect it for scoring or damage.
- Install the new square key and slide the new impeller onto the driveshaft. Ensure the blades are oriented for clockwise rotation.
- Reinstall the water pump housing, ensuring a proper seal.
- Reattach the lower unit, refill the gear oil with a new gasket, and reconnect the spark plug wires.
- Test the engine in water, confirming a steady stream ejects from the tell-tale port.
Troubleshooting & FAQ
How do I know if this impeller fits my specific engine?
The best way to confirm fitment is to check your original part number against the references in our Part Number Matrix. Additionally, review the Engine & Model Compatibility table and compare the technical specifications and product images to your old part.
What are the signs of a failing water pump impeller?
Common symptoms include a weak or intermittent stream from the tell-tale (water outlet), engine overheating alarms, or visible cracks, stiffness, or missing blades on the old impeller upon inspection.
How often should I replace my impeller?
For most recreational boaters, it is recommended to inspect the impeller annually and replace it every 1-2 years or every 100-200 hours of use, whichever comes first. This interval can be shorter if operating in sandy or silty water.
Does this impeller come with the key?
Yes, this kit includes both the water pump impeller and the required square key for proper installation on the driveshaft.
Is the rotation direction important?
Yes, very. This is a clockwise rotation impeller. When installing, you must slide the impeller down while turning the driveshaft clockwise to ensure the blades are correctly oriented inside the pump housing.
Is this an OEM or aftermarket part?
This is a high-quality aftermarket replacement part, not an original equipment manufacturer (OEM) component. It is engineered to meet or exceed OEM specifications using comparable materials. All our parts are manufactured in an ISO 9002 certified facility and are batch-inspected for quality control.
How fast is shipping?
We offer fast worldwide shipping, with typical transit times of 5–15 days for most regions. Standard shipping is free. If available for your location, expedited shipping options will be presented at checkout.
What is the warranty and return policy?
This product is covered by a 1-year warranty against any manufacturing defects under normal operating conditions. Should an issue arise, please contact our support team with your order details. Returns are accepted for unused items in their original condition within our standard return window. Please see our policy page or contact us 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.
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.
