Oberdorfer 405M-4-12N18Bct – 1 HP 12V DC Bronze Flexible Impeller Pump and Motor Unit
The Oberdorfer 405M-4-12N18Bct is a close-coupled bronze flexible impeller pump paired with a 1 horsepower, 1800 RPM, 12-volt DC, Totally Enclosed Fan Cooled (TEFC) motor. Built from high-quality bronze throughout, with a stainless steel shaft and a durable neoprene impeller, this unit is designed for dependable fluid transfer in environments where corrosion resistance and DC power availability matter most. The 1-inch NPT inlet and discharge ports accommodate a wide range of plumbing configurations, making installation straightforward in a variety of settings. With a self-priming capability of up to 15 feet of suction lift when fully primed, this pump is ready to work without complicated setup.
What makes the 405M design stand out is its simplicity — there is only one moving part, the flexible impeller, which is self-lubricating as long as liquid is present. The flexible blades generate pumping action by continuously squeezing fluid into the discharge port as the impeller rotates around an offset cam. This design eliminates metal-to-metal contact and the noise and wear that come with it. The pump can also be throttled or briefly shut off without requiring a relief valve. Because the 405M-4-12N18Bct runs on 12 volts DC, it is well suited for applications powered by battery banks, generator sets, DC distribution panels, or any 12-volt power source — making it a practical choice for mobile, remote, and off-grid fluid transfer tasks well beyond the marine world.
Key Features
- All-bronze pump body construction for maximum corrosion resistance
- Stainless steel shaft for long-term reliability
- Neoprene flexible impeller — single moving part design
- Close-coupled to a 1 HP, 12V DC, TEFC (Totally Enclosed Fan Cooled) motor
- Mechanical seal with Buna elastomer
- Self-priming capability up to 15 feet of suction lift (when fully primed)
- Easy impeller replacement — fully field-serviceable
- No metal-to-metal pumping action — no gears to jam or clog
- Flow can be throttled or shut off briefly without a relief valve
- Optional vacuum switch shut-off available
- Optional Nitrile (Buna N) impeller available for oil-contaminated water or kerosene service
Applications
- General fluid transfer and portable utility pumping
- Water supply from tanks, cisterns, or storage vessels
- Irrigation system filling and transfer
- Mobile or remote-site water delivery
- Campsite, trailer, and mobile home water/waste transfer
- Emergency and backup pumping
- Washdown service
- Holding tank pumpout
- Baitwell and aquaculture recirculation
- Mild chemical solution transfer (compatible with neoprene)
- Flood response and emergency dewatering
- RV and off-grid system fluid management
Specifications
- Part Number: 405M-4-12N18Bct
- Pump Body Material: Bronze
- Shaft Material: Stainless Steel
- Impeller Material: Neoprene (Nitrile/Buna N optional)
- Seal Type: Mechanical seal with Buna elastomer
- Motor Power: 1 Horsepower (HP)
- Motor Speed: 1800 RPM
- Motor Voltage: 12 Volts DC
- Motor Enclosure: TEFC (Totally Enclosed Fan Cooled)
- Motor Frame: NEMA 56C
- Port Size (Inlet): 1 inch NPT / 1-1/2 inch Hose
- Port Size (Outlet/Discharge): 1 inch NPT / 1-1/2 inch Hose
- Max Flow Rate: Up to 25 GPM (at low head)
- Self-Priming Suction Lift: Up to 15 feet (primed)
- Temperature Range (Neoprene Impeller): 45°F to 180°F (7°C to 82°C)
- Drive Configuration: Close-coupled (direct drive, no shaft coupling)
- Compatible Fluids: Fresh water, salt water, mild water-based solutions
- Not Suitable For: Gasoline, severe solvents, acids, viscous oils
Frequently Asked Questions
Q: Does this pump require AC power or can it run on a battery?
This pump is powered by a 12-volt DC motor, so it runs directly from a 12-volt battery, battery bank, or any properly rated 12V DC power source. No inverter or AC power supply is needed, which makes it convenient for vehicles, trailers, remote sites, and any off-grid application.
Q: What happens if the pump runs dry?
Running the 405M-4-12N18Bct dry will rapidly degrade the flexible neoprene impeller, because the impeller depends on the pumped liquid for lubrication. Always prime the pump before startup and ensure a continuous liquid supply during operation. If the pump has been idle for an extended period, the impeller should be removed to prevent the blades from taking a permanent set.
Q: Can the impeller be replaced in the field without sending the pump in for service?
Yes. Oberdorfer designed the 405M series to be completely field-serviceable. Replacing the impeller involves removing the cover screws, pulling the cover, and extracting the impeller — typically with a pair of pliers or two flathead screwdrivers. The new impeller is installed by aligning the keyway, applying a small amount of oil to the shaft, and pressing it into place carefully. No specialized tools or shop equipment are required.
Q: Is this pump bidirectional, and does the direction of rotation matter?
The 405M flexible impeller pump can operate in either rotational direction, and the direction of shaft rotation determines which port functions as the inlet and which as the outlet. However, the pump should be set to a consistent rotational direction during operation — switching direction mid-operation is not recommended.
Q: Can this pump handle fluids other than water?
With its standard neoprene impeller, the 405M-4-12N18Bct handles fresh water, salt water, and mild water-based solutions effectively. If oil-contaminated water or kerosene transfer is needed, an optional Nitrile (Buna N) impeller can be used, though at a reduced service life. Gasoline, severe solvents, acids, and viscous oils are not compatible with this pump in any impeller configuration.
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