Impeller Kit – Fits Westerbeke Marine Generators 3.3-15.0kW (Replaces 034440, 34440, Sierra 23-3307)
Impeller Kit – Fits Westerbeke Marine Generators 3.3-15.0kW (Replaces 034440, 34440, Sierra 23-3307) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
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Impeller Kit – Fits Westerbeke Marine Generators 3.3-15.0kW (Replac...
Impeller Kit – Fits Westerbeke Marine Generators 3.3-15.0kW (Replaces 034440, 34440, Sierra 23-3307) is backordered and will ship as soon as it is back in stock.
Product Details
This Impeller Kit – Fits Westerbeke Marine Generators 3.3-15.0kW (Replaces 034440, 34440) is engineered for a precise fit on Westerbeke marine generators from 3.3kW to 15.0kW (50/60Hz) that utilize the 33636 sea water pump. Critically, it is compatible only with pumps that have an irregular-shaped cover and were manufactured prior to March 2004.
It serves as a direct replacement for Westerbeke part numbers 034440 and 34440, as well as Sierra 23-3307.
- Designed for raw water pump installations in marine environments.
- The neoprene impeller is built for durability and efficient water flow.
- Kit includes the impeller, gasket, and mounting screws for a complete service.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket brands.
| Brand | Part Number |
|---|---|
| Westerbeke | 034440 |
| Westerbeke | 34440 |
| Sierra | 23-3307 |
Engine & Model Compatibility
Confirm your engine model and year in the table below. This part is specific to models equipped with the pre-March 2004 sea water pump 33636 (irregular cover).
| Model | Rated kW | Frequency | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|
| 3.3 WMD | 3.3kW | 50Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 4.0 BCD | 4.0kW | 60Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 4.0 BCD | 4.0kW | 50Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 4.0 BCDA | 4.0kW | 50Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 4.0 BCDB | 4.0kW | 50Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 4.4 BCD | 4.4kW | 60Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 4.4 WMD | 4.4kW | 60Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 4.5 BCD | 4.5kW | 50Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 5.0 BCD | 5.0kW | 60Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 5.0 BCDA | 5.0kW | 60Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 5.0 BCDB | 5.0kW | 60Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 5.7 BTD | 5.7kW | 50Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 5.8 WMD | 5.8kW | 50Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 6.0 BTD | 6.0kW | 50Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 6.0 BTDA | 6.0kW | 50Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 6.0 WMD | 6.0kW | 50Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 7.5 BTD | 7.5kW | 50Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 7.5 BTDA | 7.5kW | 50Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 7.6 BTD | 7.6kW | 60Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 7.7 WMD | 7.7kW | 60Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 8.0 BTD | 8.0kW | 60Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 8.0 BTDA | 8.0kW | 60Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 8.0 WMD | 8.0kW | 60Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 8.3 BTD | 8.3kW | 50Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 8.3 WMD | 8.3kW | 50Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 9.4 BTD | 9.4kW | 50Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 9.4 BTDA | 9.4kW | 50Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 9.4 BTDB | 9.4kW | 50Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 9.4 WMD | 9.4kW | 50Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 10.0 BTD | 10.0kW | 60Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 10.0 BTDA | 10.0kW | 60Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 11.0 BTD | 11.0kW | 60Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 11.0 WMD | 11.0kW | 60Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 12.0 BTDC | 12.0kW | 50Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 12.5 BTD | 12.5kW | 60Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 12.5 BTDA | 12.5kW | 60Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 12.5 BTDB | 12.5kW | 60Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 12.5 WMD | 12.5kW | 60Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
| 15.0 BTDC | 15.0kW | 60Hz | Up to 2004 | 034440 | For pumps with irregular cover only |
Technical Specs
- Product Type
- Water Pump Impeller Kit
- Installation
- Raw Water/Sea Water Pump
- Impeller Material
- Neoprene
- Drive Type
- Slotted Shaft Pin Drive
- Number of Blades
- 6
- Impeller Height
- 22 mm (0.88 inch)
- Overall Diameter
- 50.8 mm (2 inches)
- Shaft Diameter
- 12 mm (0.47 inch)
- Housing Compatibility
- Irregular Cover Only (Pre-March 2004)
- Pump Application
- Sea Water Pump Number 33636
What’s in the Box
- 1 x Water Pump Impeller (034440)
- 1 x Pump Cover Gasket
- 2 x SS Hex/Slot Screws
Installation Notes
This impeller kit is only for Westerbeke 33636 sea water pumps with an irregular cover, manufactured before March 2004. Do not use on pumps with a round cover and O-ring seal; those require impeller kit 48500. Before installation, shut off the engine and close the seacock. Lubricate the new impeller and the inside of the pump housing with a suitable marine lubricant to prevent damage during initial startup.
Troubleshooting & FAQ
How do I know if this impeller fits my generator?
Verify your generator is listed in the compatibility table. Most importantly, check that your sea water pump is model 33636 and has an irregular-shaped cover held on by screws. If your pump cover is round and uses an O-ring, this part will not fit.
What is the difference between this kit and one for newer models?
This kit is for pre-March 2004 pumps with an "irregular" cover. Newer Westerbeke pumps often use a round cover with an O-ring, which requires a different impeller and seal (like kit 48500). The physical dimensions and included gasket are specific to the older pump design.
How often should I replace my water pump impeller?
As a general rule, impellers should be inspected annually and replaced every 1-2 years or every 200-300 hours of operation, whichever comes first. Harsh operating conditions (sandy or silty water) may require more frequent replacement.
What are the signs of a failing impeller?
Common symptoms include engine overheating at idle or low speeds, reduced water flow from the exhaust outlet, and visible cracks or missing blades on the impeller itself upon inspection. A complete failure can cause rapid overheating and serious engine damage.
Is the included gasket necessary?
Yes. The gasket is critical for creating a watertight seal between the pump housing and the irregular cover plate. Never reuse an old gasket, as it may be compressed or cracked, leading to leaks.
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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