Overflow Tank Radiator 4in x 8in with Hardware

The Overflow Tank Radiator 4in x 8in with Hardware from Specialty Products Company is purpose-built for marine cooling systems that demand reliability under variable water conditions and engine loads. Whether you're running a saltwater sportfish rig or a freshwater cruiser, this compact overflow reservoir handles thermal expansion and coolant loss with straightforward, proven engineering. Boaters operating in demanding conditions—long offshore runs, high-RPM cruising, or tropical climates—rely on this tank to prevent air locks, cavitation, and overheating that can strand you miles from port.

This overflow tank features a polished stainless-steel construction that resists corrosion in saltwater environments and maintains visibility of coolant levels throughout your trip. The 20-ounce capacity with 8-inch height fits tight engine compartments while providing sufficient volume to manage thermal cycling without overflow into the bilge. Dual 5/16-inch hose barb connections—one for inlet flow and one for petcock drain—ensure secure, leak-free attachment to your cooling loop and enable straightforward fluid changes when needed. The included mounting hardware simplifies installation, allowing you to integrate this tank into existing or new cooling systems without custom fabrication.

Inboard and outboard applications, diesel or gasoline, benefit from the overflow tank's ability to stabilize coolant temperature and prevent vapor lock during high-load operation. The compact 3.7 x 3.55-inch footprint (11.15 inches tall) slides into limited spaces found aboard most pleasure and working vessels. Installation is straightforward: mount near the high point of your cooling system, connect the inlet to the radiator filler neck, and route the drain back to the reservoir. Regular inspection of the stainless tank ensures long-term durability and gives you confidence that your cooling system is protected, whether you're docked or pushing offshore.