Sierra Marine Circulating Water Pump 18-3575 – MerCruiser / Volvo Penta / OMC GM 4 & 6 Cylinder
Free returns on all eligible orders
You have 30 days to request a return. All sale items are final sale.
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Alternate / Superseded Part Numbers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)
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.