Circulating Water Pump – Fits MerCruiser, Volvo Penta 4.3–6.3L Marine Engines (Replaces 8M0113734, 3853850)
Circulating Water Pump – Fits MerCruiser, Volvo Penta 4.3–6.3L Marine Engines (Replaces 8M0113734, 3853850) 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
Circulating Water Pump – Fits MerCruiser, Volvo Penta 4.3–6.3L Mari...
Product Details
This bi-directional Circulating Water Pump – Fits MerCruiser, Volvo Penta 4.3–6.3L Marine Engines (Replaces 8M0113734, 3853850) is engineered for a wide range of marine engines, including MerCruiser 4.3L V6 to 6.3L V8 models (1963–2014), Volvo Penta 4.3L V6 to 6.3L V8 models (1973 and later), and select OMC engines (1968–1998).
It serves as a direct interchange for MerCruiser 8M0113734/8503991, Sierra 18-3599-2/18-3599-1/18-3583, Volvo Penta 3853850, Crusader 20318/7142520, and Pleasurecraft RA057018.
- Installs directly to the engine block.
- Features bi-directional flow, making it compatible with both steel and composite timing chain covers.
- Includes the necessary mounting gaskets for a complete installation.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket brands.
| Brand | Part Number |
|---|---|
| MerCruiser | 8M0113734 |
| MerCruiser | 8503991 |
| Sierra | 18-3599-2 |
| Sierra | 18-3599-1 |
| Sierra | 18-3583 |
| Volvo Penta | 3853850 |
| OMC | 382218 |
| OMC | 980477 |
| OMC | 985429 |
| Crusader | 20318 |
| Crusader | 7142520 |
| Pleasurecraft | RA057018 |
Engine & Model Compatibility
Confirm your engine model and year range in the tables below to ensure proper fitment.
MerCruiser Applications: Fits a wide range of V6 and small block V8 engines from 1963 to 2014. Note the exception for 2007+ V6 engines, which must have a water bypass hole.
Volvo Penta Applications: Compatible with GM-based V6 and small block V8 engines manufactured from 1973 onwards.
OMC Applications: Designed for small block V6 and V8 engines produced between 1968 and 1998.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| MerCruiser | 4.3L V6 | 140-200 | 4-Stroke | 1963–2014 | 8503991/8M0113734 | Will NOT fit 2007+ V6 4.3L engines without water bypass hole |
| MerCruiser | 5.0L V8 | 155-205 | 4-Stroke | 1963–2014 | 8503991/8M0113734 | Small block applications |
| MerCruiser | 5.7L V8 | 230-260 | 4-Stroke | 1963–2014 | 8503991/8M0113734 | Small block applications |
| MerCruiser | 6.2L V8 | 4-Stroke | 8503991/8M0113734 | Small block applications | ||
| MerCruiser | 6.3L V8 | 4-Stroke | 8503991/8M0113734 | Small block applications | ||
| Volvo Penta | GM 4.3L | 4-Stroke | 1973 and later | 3853850 | V6 engine | |
| Volvo Penta | GM 5.0L | 4-Stroke | 1973 and later | 3853850 | Small block V8 | |
| Volvo Penta | GM 5.7L | 4-Stroke | 1973 and later | 3853850 | Small block V8 | |
| Volvo Penta | GM 6.2L | 4-Stroke | 1973 and later | 3853850 | Small block V8 | |
| Volvo Penta | GM 6.3L | 4-Stroke | 1973 and later | 3853850 | Small block V8 | |
| OMC | V6/V8 Small Block | 4-Stroke | 1968–1998 | 382218/3853850/980477/985429 | Small block applications | |
| Crusader | Small Block V6/V8 | 4-Stroke | 20318/7142520 | Small block applications | ||
| Indmar | Small Block V6/V8 | 4-Stroke | Small block applications | |||
| Pleasurecraft | Small Block V6/V8 | 4-Stroke | RA057018 | Small block applications | ||
| Marine Power | V6/V8 | 4-Stroke | Small block applications | |||
| PCM | V6/V8 | 4-Stroke | Small block applications |
Technical Specs
- Product Type
- Bi-Directional Water Circulating Pump
- Installation
- Engine mounted
- Connection
- Threaded ports with brass fittings
- Housing Material
- Cast steel with stainless steel backing plate
- Housing Color
- Black
- Weight
- 4.55 kg (9.92 lb)
- Fitting Type
- Brass fittings with hose connections
- Key Feature
- Bi-directional flow, compatible with steel and composite timing chain covers
- Warranty
- Varies by manufacturer (6 months to lifetime depending on brand)
What’s in the Box
- 1 x Water Circulation Pump (Replaces 8503991/8M0113734)
- 1 x Mounting Gaskets (Replaces 18-0891)
Installation Notes
- Disconnect the negative battery terminal.
- Drain the engine coolant into a suitable container.
- Loosen the serpentine belt and remove it from the pump pulley.
- Remove any brackets or components obstructing access to the pump.
- Disconnect the coolant hoses from the pump.
- Remove the mounting bolts holding the old water pump to the engine block.
- Carefully detach the old pump and gasket. Thoroughly clean the mounting surface on the engine block to remove all old gasket material.
- Position the new gasket and water pump onto the engine block.
- Install and hand-tighten the mounting bolts, then torque them to the manufacturer's specified sequence and values.
- Reconnect coolant hoses and any removed brackets.
- Reinstall the serpentine belt, ensuring it is routed correctly and tensioned properly.
- Refill the cooling system with the appropriate coolant, reconnect the battery, and start the engine to check for leaks and proper operation.
Troubleshooting & FAQ
Will this pump fit a 2008 MerCruiser 4.3L V6?
No. This pump is not compatible with 2007 and newer MerCruiser V6 4.3L engines that do not have a water bypass hole. Please verify your specific engine configuration before ordering.
Is this a bi-directional pump?
Yes, this is a bi-directional circulating pump. It is designed to work correctly with engines that have either steel or composite timing chain covers, ensuring proper coolant flow regardless of rotation.
What are the signs of a failing water pump?
Common symptoms of a bad water pump include engine overheating at low speeds, coolant leaks from the pump's weep hole or gasket, a wobbly or noisy pump pulley, or a grinding sound from the pump assembly.
How often should I replace my marine water pump?
Replacement intervals depend on factors like saltwater versus freshwater use and engine hours. As a general guideline, inspect the pump annually and consider preventative replacement every 300-500 operating hours or every 3-5 years to avoid engine damage.
Is this an OEM part?
This listing is an aftermarket replacement, not an OEM component. It has been manufactured in an ISO 9002 facility to meet or exceed original equipment specifications, using comparable materials and undergoing batch-inspections for quality assurance.
How much is shipping and how fast is it?
We ship worldwide, with most orders arriving in 5–15 days. Standard shipping is free for most regions. Expedited shipping options, if available for your location, will be presented at checkout.
What is the warranty and return policy?
This product is covered by a 1-year warranty against manufacturing defects under normal marine use. If you encounter an issue, please contact our support team with your order details. Returns are accepted within our standard window for items that are unused and in their original packaging. Refer to our policy page or contact us for complete instructions.
Safety & Important Info
- Verify images and specifications against your original part before purchasing. If anything differs—even if your model is listed as compatible—do not order.
- This is an aftermarket replacement part, not an original equipment manufacturer (OEM) component.
- Professional installation is strongly recommended to ensure safety, proper function, and longevity.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and rigorously tested for real-world reliability.
- Fast Global Fulfillment — We offer free standard delivery to most regions, with typical transit times of 5–15 days.
- Manufacturer-Direct Value — By working directly with manufacturers, we provide fair pricing without compromising on materials or quality control.
Payment & Security
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