Bi-Directional Water Pump – Fits MerCruiser, Volvo Penta 4.3L, 5.0L, 5.7L V6/V8 (Replaces 8503991, 8M0113734)

Bi-Directional Water Pump – Fits MerCruiser, Volvo Penta 4.3L, 5.0L, 5.7L V6/V8

This engine-mounted, bi-directional water circulating pump is designed for a wide range of MerCruiser, Volvo Penta, and OMC small block V6/V8 engines. It ensures reliable coolant flow in either direction and is compatible with both steel and composite timing chain covers.

It serves as a direct replacement for MerCruiser parts 8503991 and 8M0113734, Volvo Penta 3853850, Sierra 18-3599-1 and 18-3599-2, Crusader 20318 and 7142520, and Pleasurecraft RA057018.

• Installation: Engine mounted
• Housing: Cast steel with a stainless steel backing plate for corrosion resistance.
• Fittings: Includes brass fittings for hose connections.

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below.

MerCruiser

Volvo Penta

Other Manufacturers

Technical Specifications

Package Contents

• 1 x Water Circulation Pump (Replaces 8503991/8M0113734)

Installation Guide

Professional installation is recommended. The following are general steps and may not be exact for your specific engine model.

1. Disconnect the battery and drain the cooling system completely.
2. Loosen the alternator and remove the drive belts from the pump pulley.
3. Remove the pulley from the old water pump.
4. Disconnect the radiator and heater hoses from the water pump.
5. Remove the bolts securing the old water pump to the engine block and carefully remove the pump.
6. Clean the gasket mating surfaces on the engine block, removing all old gasket material and sealant.
7. Apply a thin layer of gasket sealant to the new gasket and place it on the new water pump.
8. Mount the new water pump onto the engine, ensuring the gasket is properly aligned.
9. Tighten the mounting bolts to the manufacturer's specified torque.
10. Re-attach the hoses, pulley, and drive belts. Tension the belts correctly.
11. Reconnect the battery and refill the cooling system with the appropriate coolant mixture.
12. Start the engine, check for leaks, and top off the coolant as needed after the engine reaches operating temperature.

Troubleshooting & FAQ

How do I confirm this pump fits my 4.3L V6 engine?
This pump fits MerCruiser 4.3L V6 engines made between 1963-2007. However, it will NOT fit models made after 2007 that do not have a water bypass hole. Please verify your engine specifications before ordering.

What is a bi-directional pump, and why is it important?
A bi-directional pump can circulate coolant effectively regardless of the engine's rotation direction. This makes it versatile for use in various standard and reverse-rotation marine engines.

What are common signs that my water pump is failing?
Common signs include the engine overheating, coolant leaks from the pump housing (often from the weep hole), a noisy or grinding sound from the pump bearing, or a loose pulley.

OEM vs. Aftermarket?
This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

How fast do you ship and how much does it cost?
We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

What is your warranty and return policy?
This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.