Bi-directional Water Pump – Fits Volvo Penta 4.3L-6.3L V6/V8 (Replaces 3853850, 18-3599-1)
Bi-directional Water Pump – Fits Volvo Penta 4.3L-6.3L V6/V8 (Replaces 3853850, 18-3599-1) is backordered and will ship as soon as it is back in stock.
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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
Bi-directional Water Pump – Fits Volvo Penta 4.3L-6.3L V6/V8 (Repla...
Product Details
This Bi-directional Water Pump is a direct-fit circulating pump for a wide range of Volvo Penta marine engines. It is specifically designed for GM-based V6 and V8 models from 4.3L to 6.3L, including inboard and sterndrive applications.
It serves as a direct replacement for numerous OEM and aftermarket part numbers, including Volvo Penta 3853850, Sierra 18-3599-1, MerCruiser 8503991, OMC 985429, and Pleasurecraft RA057018.
- Installs as a direct bolt-on replacement.
- Bi-directional design works for both standard and counter-rotating engines.
- Fits both composite and steel timing covers for broad compatibility.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Notes |
|---|---|---|
| Volvo Penta | 3853850 | |
| Sierra | 18-3599-1 | Superseded by 18-3599-2 |
| Sierra | 18-3599-2 | |
| MerCruiser | 811841 | |
| MerCruiser | 850399 | |
| MerCruiser | 8503991 | |
| OMC | 985429 | |
| OMC | 3853850 | |
| OMC | 980477 | |
| OMC | 382218 | |
| Pleasurecraft | RA057018 | |
| Crusader | 7142520 | |
| Crusader | 20318 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This pump fits V6 and V8 engines from major brands including Volvo Penta, MerCruiser, OMC, Pleasurecraft (PCM), and Crusader.
| Brand | Model | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|
| Volvo Penta | GM 4.3L | 4-Stroke | 3853850 | V6 engines | |
| Volvo Penta | GM 5.0L | 4-Stroke | 3853850 | V8 engines | |
| Volvo Penta | GM 5.7L | 4-Stroke | 3853850 | V8 engines | |
| Volvo Penta | GM 6.2L | 4-Stroke | 3853850 | V8 engines | |
| Volvo Penta | GM 6.3L | 4-Stroke | 3853850 | V8 engines | |
| MerCruiser | 4.3L | 4-Stroke | 8503991, 811841, 850399 | V6 engines | |
| MerCruiser | 5.0L | 4-Stroke | 8503991, 811841, 850399 | V8 engines | |
| MerCruiser | 5.7L | 4-Stroke | 8503991, 811841, 850399 | V8 engines | |
| MerCruiser | 6.2L | 4-Stroke | 8503991, 811841, 850399 | V8 engines | |
| MerCruiser | 6.3L | 4-Stroke | 8503991, 811841, 850399 | V8 engines | |
| OMC | V6/V8 | 4-Stroke | 1968–1998 | 985429, 980477, 382218, 3853850 | Stern Drive |
| Pleasurecraft | V6/V8 | 4-Stroke | RA057018 | Small Block V6/V8 | |
| Crusader | V6/V8 | 4-Stroke | 7142520, 20318 | Small Block V6/V8 |
Technical Specs
- Product Type
- Circulating Water Pump (Bi-directional)
- Installation
- Direct bolt-on replacement
- Housing Material
- Cast metal with zinc coating
- Housing Color
- Black
- Weight
- 10.2 lbs (4.6 kg)
- Fitting Type
- Direct bolt-on
- Warranty
- 12 months
- Other Technical Attributes
- Bi-directional design works with both standard and counter-rotating engines. Fits both composite and steel timing covers.
What’s in the Box
- 1 x Bi-directional Water Pump
- 2 x Gaskets
Installation Notes
- Disconnect the battery and drain the cooling system completely.
- Loosen and remove any accessory belts connected to the water pump pulley.
- Remove all hoses connected to the water pump. Be prepared for some residual coolant spillage.
- Unbolt and carefully remove the old water pump from the engine block.
- Thoroughly clean the engine block's mating surface to remove old gasket material and residue.
- Position the new gaskets and install the new water pump, ensuring a snug fit.
- Hand-tighten the mounting bolts, then torque them to the manufacturer's specified values and sequence.
- Reconnect all hoses and reinstall the accessory belts, ensuring proper tension.
- Refill the cooling system with the appropriate coolant mixture.
- Reconnect the battery, start the engine, and carefully check for any leaks around the pump and hoses.
Troubleshooting & FAQ
How do I know if this pump fits my specific engine?
This pump fits a wide range of GM-based V6 and V8 engines (4.3L to 6.3L) used by brands like Volvo Penta, MerCruiser, and OMC. The best way to confirm fitment is to match your original part number to one of the equivalents listed in our Part Number Matrix. Also, check your engine model against the compatibility table.
What does "bi-directional" mean and why is it important?
A bi-directional pump is designed to circulate coolant effectively regardless of the engine's rotational direction. This makes it a versatile replacement for both standard (clockwise) and counter-rotating (counter-clockwise) marine engines without needing separate part numbers.
What are the common signs of a failing water pump?
Key symptoms include the engine running hotter than normal or overheating, noticeable coolant leaks from the pump's weep hole or gasket, a noisy or wobbly pulley on the front of the pump, or visible steam coming from the engine bay.
Will this pump fit both composite and steel timing covers?
Yes, this pump is engineered to mount correctly to both composite and stamped steel timing chain covers, which adds to its broad compatibility across different engine years and variations.
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.
Payment & Security
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