Sierra O/B & I/O Cooling/Water Pumps
Sierra 18-3390 Water Pump Repair Kit without Housing for Johnson/Evinrude Outboards
Sierra 18-3389 Water Pump Repair Kit with Housing for Johnson/Evinrude Outboards
Sierra 18-3314 Marine Water Pump Kit with Housing for Mercury/Mariner Outboards
Sierra O/B & I/O Cooling Water Pumps: Keeping Your Engine Cool on the Water
The raw water cooling system is the lifeline of any marine engine — and the water pump is its beating heart. Whether you run an outboard, a sterndrive, or a traditional inboard/outdrive setup, a failing pump means one thing: overheating, and potentially catastrophic engine damage. Sierra has spent more than 58 years engineering water pumps and cooling components that boaters and marine technicians depend on to keep engines running in the harshest saltwater and freshwater environments.
Why Sierra Leads in Marine Water Pump Reliability
OEM-level engineering, aftermarket value. Sierra's water pumps and cooling kits are precisely matched to specific engine platforms — GM, Ford, and Chrysler-based inboard blocks, as well as today's most popular outboard brands including Mercury/Mariner, Yamaha, Johnson/Evinrude, and Volvo Penta. Each pump is engineered to meet or exceed original manufacturer specifications, and Sierra's track record of supplying parts directly to OEM engine manufacturers and boat builders speaks to the quality of their components.
For inboard and I/O applications, Sierra's O/B & I/O cooling water pumps are designed to be bidirectional, making them compatible with both conventional and reverse-rotation engines — an important consideration when servicing a wide range of sterndrive configurations. The water pump assemblies feature corrosion-resistant brass impellers, stainless steel backing plates and seal cups, powder-coated housings for added protection against the marine environment, and all necessary mounting gaskets and hardware for a complete, no-surprises installation.
Outboard cooling kits cover an extensive range of engine families, from small 2-cylinder, 5–15 HP Johnson/Evinrude mills all the way up to high-output V6 and V8 outboards. MerCruiser Alpha One, Alpha Gen II, and Bravo sterndrive owners will find dedicated kits engineered specifically for their drive configurations. Whether you need a full water pump housing kit or a service/repair kit to rebuild an existing pump, Sierra offers both options across dozens of fitments.
What's Typically Included in a Sierra Water Pump Kit
- Impeller (rubber neoprene or brass, application-dependent)
- Pump housing or body (where applicable)
- Faceplate and backing plate
- Drive key and water tube seal
- O-rings, gaskets, and all necessary attaching hardware
- Stainless steel seal cup and spring (on select models)
Sierra's Warranty Commitment
One of the standout differentiators in the marine aftermarket world is Sierra's unconditional warranty. Should a warrantied part fail, Sierra covers not just the part itself but also associated shop labor, haul-out, and towing fees — a level of confidence that reflects decades of precision engineering and real-world testing. For a boater who depends on their vessel, that kind of backing is invaluable.
When it's time to service your outboard or sterndrive cooling system, trust the brand that marine professionals rely on. Browse the full selection of O/B & I/O Cooling Water Pumps to find the exact kit for your engine, or explore everything Sierra offers across the full spectrum of marine engine parts.
