Description

The 66DX35G1I is a high-performance, hollow-shaft plunger pump manufactured by Cat Pumps. It is a staple in the industrial pressure washing industry, specifically designed to bolt directly onto gasoline engines with a 1″ horizontal shaft.

This “I” model is a comprehensive package, meaning it comes factory-equipped with a regulated unloader and a bypass hose, making it a “drop-in” solution for pump replacements.

Technical Specifications

• Flow Rate: $3.5\ \text{GPM}$ (Gallons Per Minute).

• Max Pressure: $4000\ \text{PSI}$.

• Inlet Port: $1/2″\ \text{NPT(F)}$.

• Discharge Port: $3/8″\ \text{NPT(M)}$.

• Shaft Diameter: $1″$ (Hollow shaft for gas engine mounting).

• RPM: $3400\ \text{RPM}$ (Matches standard gas engine speeds).

• Weight: Approximately 26 lbs.

Key Features

• Built-in Unloader (W/UNL): Features an integral pressure-regulating unloader. This bypasses water flow when the trigger gun is released, protecting the pump from over-pressurization.

• Ceramic Plungers: Solid chemical-resistant ceramic plungers provide a smooth wear surface and extended seal life.

• Dual Oil Seals: Specialized seals prevent oil leaks and protect the crankcase from water contamination.

• Forged Brass Manifold: Provides high strength and superior corrosion resistance under the intense $4000\ \text{PSI}$ load.

Primary Application

• Direct Drive Gas Engines: Typically paired with 11HP to 13HP engines (like the Honda GX390). Because it is a direct-drive pump, it is more compact and easier to maintain than belt-drive systems, though it runs at higher speeds.

Maintenance & Operation Tips

• Oil Changes: Use Cat Pump Custom Lubricant (ISO 68). Change the initial fill after the first 50 hours of operation, then every 500 hours or every 3 months thereafter.

• Bypass Safety: Do not leave the pump in “bypass mode” (engine running but trigger not pulled) for more than 2–3 minutes. The water inside the pump will rapidly heat up and can damage the seals.

• Inlet Water Supply: Ensure your water source provides at least $7\ \text{GPM}$ (double the pump’s output) to prevent cavitation, which sounds like “marbles” rattling in the pump and causes immediate internal damage.

• Winterization: Always blow out the water or use pump protector if storing the unit in freezing temperatures; the brass manifold can crack if water freezes inside.