Sierra Marine Circulating Water Pump 18-3575 MerCruiser / Volvo Penta / OMC GM 4 & 6 Cylinder

The Sierra 18-3575 Circulating Water Pump is a complete, engine-mounted cooling pump designed for GM-based inline 4-cylinder and 6-cylinder marine engines used in MerCruiser, Volvo Penta, and OMC applications.

This pump is responsible for circulating coolant (or raw water in open systems) through the engine block, maintaining proper operating temperature and preventing overheating.

This is a belt-driven circulating pump, not a raw water impeller kit. It is a critical component of the engine cooling system and is commonly replaced when experiencing overheating, bearing failure, or coolant leaks.

Built from new castings and engineered to meet or exceed OEM specifications, this pump delivers reliable performance and long service life in marine environments.

Key Features

• Complete circulating water pump assembly
• Engine-mounted, belt-driven design
• Bi-directional (fits standard & reverse rotation engines)
• Restores proper coolant circulation
• Marine-grade corrosion-resistant construction
• Built from new castings (not remanufactured)
• Sierra limited lifetime warranty

Engine Compatibility

MerCruiser (GM Inline Engines)

• 2.5L (4 cylinder)
• 3.0L (4 cylinder)

Volvo Penta

• 3.0L 4-cylinder engines

OMC / Cobra / Inboard

• GM-based inline 4 & inline 6 cylinder engines

Designed specifically for GM inline marine engine platforms

Serial Number Fitment Notice

Fitment depends on:

• Engine model and year
• Pulley alignment
• Mounting configuration

Always confirm compatibility using engine serial number before ordering.

When This Part Needs Replacement

Replace the circulating pump if you notice:

• Engine overheating at all RPM ranges
• Coolant or water leaking from weep hole
• Bearing noise or pulley wobble
• Reduced coolant flow
• Corrosion or internal wear

Installation Notes

• Verify pulley alignment before install
• Replace mounting gasket
• Inspect belts and tensioners
• Torque bolts evenly to spec
• Prime cooling system before startup

Alternate / Superseded Part Numbers

OEM Cross References

• Mercury / MerCruiser: 65142A1, 880817, 884727
• Volvo Penta: 3854017
• OMC: 380640, 984360, 986779, 3854017, 3858340

Aftermarket Cross References

• Mallory: 9-42605
• GLM: 15100
• Pro Marine: 64727
• Redline: RL3575

Shipping

Shipping: Ships same or next day for fast Canada wide shipping.

Parts Desk Insight

This is one of the most commonly mis-listed parts online as a kit.

Key difference:

• 18-3575 = circulating pump (engine front)
• Impeller kits = in the drive / lower unit

Good bundle:

• Thermostat + gasket
• Raw water pump impeller kit
• Full cooling service package (high conversion on 3.0L boats)