Bi-Directional Circulating Water Pump for GM V6 & Small-Block V8 Marine Engines – Replaces 8503991, 8M0113734, 3853850
Bi-Directional Circulating Water Pump for GM V6 & Small-Block V8 Marine Engines – Replaces 8503991, 8M0113734, 3853850 is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
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Bi-Directional Circulating Water Pump for GM V6 & Small-Block V...
Bi-Directional Circulating Water Pump for GM V6 & Small-Block V8 Marine Engines – Replaces 8503991, 8M0113734, 3853850 is backordered and will ship as soon as it is back in stock.
Product Details
This engine-mounted bi-directional circulating water pump is an aftermarket replacement for selected GM-based marine cooling systems. Catalog references identify this pump family for GM V6 and small-block V8 engines, including 4.3L, 5.0L, and 5.7L applications, and for compatible Volvo Penta marine applications using the same water-pump pattern.
The pump is designed to circulate engine coolant through the block and cooling system. Its bi-directional design supports compatible standard- and reverse-rotation applications and works with both metal and composite timing-chain covers when the engine configuration matches.
- Engine-mounted circulating water pump for selected marine GM V6 and small-block V8 applications.
- Bi-directional design for compatible rotation configurations.
- Suitable for applications using metal or composite timing-chain covers where specified.
- Replacement gasket is included for the listed pump application.
Part Number Matrix
Use the following references as interchange leads only. Always compare the original pump, mounting arrangement, gasket pattern, timing-chain cover, and engine serial information before ordering.
| Brand or Source | Reference Number | Relationship |
|---|---|---|
| MerCruiser / Mercury Marine | 8503991 | OEM reference |
| MerCruiser / Mercury Marine | 8M0113734 | OEM reference |
| Volvo Penta | 3853850 | OEM reference |
| Sierra | 18-3599-1 | Aftermarket interchange reference |
| Sierra | 18-3599-2 | Aftermarket interchange reference |
| Crusader | 20318 | Aftermarket interchange reference |
| Crusader | 7142520 | Aftermarket interchange reference |
| Pleasurecraft | RA057018 | Aftermarket interchange reference |
Engine & Model Compatibility
The references below describe the documented engine families and applications associated with this pump style. Exact fitment can vary by engine year, serial range, rotation, timing-chain cover, and bypass-hole configuration.
| Engine Family | Displacement Examples | Stroke | Application Notes | Reference |
|---|---|---|---|---|
| GM V6 | 3.8L, 4.3L | 4-Stroke | Small-block marine applications; verify pump pattern and timing-chain cover. | 3853850 |
| GM small-block V8 | 5.0L, 5.7L | 4-Stroke | Compatible applications may use metal or composite timing-chain covers. | 3853850 |
| Volvo Penta GM-based engines | 4.3L, 5.0L, 5.7L and related applications | 4-Stroke | Confirm the exact model, serial range, rotation, and mounting configuration. | 3853850 |
| Crusader / Pleasurecraft applications | Selected GM V6 and small-block V8 engines | 4-Stroke | Use the listed reference number and compare the original component before purchase. | 20318, 7142520, RA057018 |
Important: Do not rely on horsepower or model year alone to confirm fitment. Some later 4.3L V6 configurations may use a different cooling-pump arrangement or may lack the required water-bypass opening. Verify the engine casting, pump flange, gasket pattern, rotation, and timing-chain cover before ordering.
Technical Specs
- Product Type
- Bi-directional engine-mounted circulating water pump
- Application
- Selected GM V6 and small-block V8 marine cooling systems
- Compatible Reference
- MerCruiser 8503991 and 8M0113734; Volvo Penta 3853850
- Flow Direction
- Bi-directional
- Timing-Chain Cover Compatibility
- Metal and composite covers where specified by the engine application
- Installation
- Engine mounted
- Gasket
- Included for the documented pump application
- Construction Details
- Catalog descriptions for this pump style identify a stainless-steel backing plate, machined brass impeller, painted pump housing, and stainless-steel sealing components. Confirm the supplied component before installation.
What’s in the Box
- 1 x Bi-directional circulating water pump
- 1 x Application-specific mounting gasket
Installation Notes
- Disconnect the battery and allow the engine to cool completely.
- Drain the engine coolant into a suitable container.
- Loosen the drive belt and disconnect the hoses attached to the pump.
- Remove the pump mounting bolts and carefully remove the old pump.
- Clean the engine mounting surface and remove all old gasket material and sealant.
- Compare the replacement pump, gasket, ports, and bypass openings with the original component.
- Install the supplied gasket and replacement pump. Tighten the mounting bolts to the engine manufacturer’s specifications.
- Reconnect the hoses and reinstall the drive belt with the correct tension.
- Refill the cooling system with the manufacturer-recommended coolant mixture.
- Reconnect the battery, start the engine, and check carefully for leaks, abnormal noise, and proper operating temperature.
Troubleshooting & FAQ
Is this pump bi-directional?
Yes. It is intended for compatible marine engines requiring a bi-directional circulating water pump. Confirm the engine’s rotation and pump configuration before installation.
Which engines does this pump fit?
Documented applications include selected GM V6 and small-block V8 marine engines, including common 4.3L, 5.0L, and 5.7L configurations, plus compatible Volvo Penta, Crusader, and Pleasurecraft applications. Exact fitment depends on the engine configuration and reference number.
Will this fit every 4.3L V6 engine?
No. A 4.3L designation alone does not confirm fitment. Check the engine serial range, rotation, mounting pattern, bypass opening, gasket pattern, and timing-chain cover before ordering.
Does the package include a gasket?
Yes. The listed pump application includes an application-specific mounting gasket. Confirm that the gasket matches the engine before installation.
How can I tell if the water pump is failing?
Common symptoms include overheating, coolant leakage near the pump or weep area, poor coolant circulation, bearing noise, or visible damage to the pulley, housing, impeller, or seal.
Is this an OEM pump?
No. This listing is for an aftermarket replacement. The OEM and aftermarket numbers shown above are reference numbers used to help verify application and interchange.
What should I check before ordering?
Compare the original pump’s mounting flange, hose and port locations, rotation, gasket shape, bypass opening, timing-chain cover, and all available engine identification information.
Safety & Important Information
- Allow the engine to cool fully before opening the cooling system or removing the pump.
- Use the correct coolant and follow the engine manufacturer’s bleeding and refill procedure.
- Do not rely on horsepower, year, or displacement alone to confirm fitment.
- Verify the original part and engine configuration before purchase.
- Professional installation is recommended where required by the engine manufacturer or applicable safety procedures.
About Sea Sierra
- Marine Replacement Parts — We supply replacement components for common marine engine and cooling-system applications.
- Application-Focused Information — Reference numbers and compatibility details are provided to help you compare the replacement with your original part.
- Global Fulfillment — Standard and expedited shipping options are shown at checkout where available.
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