Oberdorfer 405MG-03-UGY: 3HP Gas Engine-Driven Bronze Flexible Impeller Pump for Dependable Fluid Transfer
When you need a pump that can go where electrical power can't follow, the Oberdorfer 405MG-03-UGY is exactly the kind of workhorse you want on the job. Paired with a Briggs & Stratton 3HP gasoline engine, this close-coupled flexible impeller pump is built around an all-bronze pump body and a stainless steel shaft — a combination that has earned Oberdorfer a loyal following across agriculture, industrial facilities, and general-purpose fluid transfer operations since the company first started making pumps back in 1890. The 405MG is compact and portable by design, which means it can be moved to wherever the work is happening rather than the other way around.
The flexible neoprene rubber impeller at the heart of this pump does the heavy lifting, capable of self-priming with suction lifts up to 15 feet when fully primed and the suction line is airtight. With a rated flow capacity of 25 GPM and a 1-inch NPT inlet and outlet port, this pump handles fresh water, salt water, and mild water-based solutions with ease. One of the more practical things about the 405MG design is how simple it is to service — the impeller and cam can be replaced without special tools, which means the pump can be restored to like-new condition after extended use rather than being thrown away. For anyone running operations in remote locations or simply needing reliable liquid transfer without depending on shore power or a generator, the 405MG-03-UGY is a straightforward, proven solution.
Key Features:
- All-bronze pump body construction for long-term corrosion resistance
- Stainless steel shaft for added durability and reliability
- Briggs & Stratton 3HP gasoline engine for fully portable, power-independent operation
- Mechanical seal design (Model 405M standard configuration)
- Neoprene rubber flexible impeller; Nitrile impeller available as an option
- Self-priming capability with up to 15 feet of suction lift when fully primed
- Single moving part for straightforward, low-maintenance operation
- Impeller and cam are user-replaceable — no complete pump replacement required
- Operates in either rotational direction; direction of shaft rotation determines inlet and outlet
- Can be mounted at any angle
- Discharge may be throttled or briefly shut off without requiring a relief valve
- Optional vacuum switch shut-off available
Applications:
- Agricultural water transfer and irrigation supply
- Industrial fluid handling and general process transfer
- Construction site dewatering
- Remote location pumping where no electrical power is available
- Fresh water and salt water transfer
- Mild chemical solutions (pH range 4 to 11)
- Portable washdown and utility service
- General-purpose liquid transfer in field, farm, and facility settings
Specifications:
- Part Number: 405MG-03-UGY
- Engine: Briggs & Stratton 3HP gasoline engine
- Pump Type: Close-coupled flexible impeller (rubber impeller)
- Flow Rate: 25 GPM
- Pump Body Material: Bronze
- Shaft Material: Stainless steel
- Seal Type: Mechanical seal
- Impeller Material: Neoprene rubber (standard); Nitrile optional
- Inlet Port: 1 inch NPT / 1-1/2 inch hose
- Outlet Port: 1 inch NPT / 1-1/2 inch hose
- Maximum Suction Lift: 15 feet (when fully primed)
- Liquid Temperature Range: 40°F to 180°F (Neoprene); 40°F to 140°F recommended for general use
- Suitable Liquids: Fresh water, salt water, mild chemical solutions compatible with neoprene
- Not Suitable For: Gasoline, severe solvents, acids, viscous oils
- Drive Configuration: Close-coupled gas engine with engine-specific adapter
Frequently Asked Questions
Q: Does the Oberdorfer 405MG-03-UGY need to be primed before first use?
Yes. On initial startup, the pump must be primed before operation. Running the pump dry even briefly can cause rapid degradation of the flexible rubber impeller. A foot valve with a built-in strainer at the beginning of the suction line is strongly recommended to help maintain prime.
Q: Can this pump handle liquids other than fresh water?
The standard neoprene impeller is compatible with fresh water, salt water, and mild water-based solutions within a pH range of approximately 4 to 11. If you need to handle oil-contaminated water or kerosene, an optional nitrile impeller can be substituted, though at a reduced service life. Gasoline, severe solvents, and acids should never be pumped with this unit.
Q: What happens if the pump freezes or sits unused for an extended period?
If freezing conditions are possible, the pump should be drained by loosening the cover screws and the chamber filled with a methyl alcohol-based antifreeze such as Zerex or Dowgard. For long storage periods, removing the impeller is also recommended to prevent it from taking a permanent set inside the housing.
Q: Is the impeller replaceable without sending the pump in for service?
Yes. One of the practical advantages of the Oberdorfer 405M design is that the impeller and cam are user-replaceable with basic hand tools. Removing the cover screws and carefully pulling the impeller with nose pliers or two flat-blade screwdrivers is all that is required. Replacement restores the pump to like-new performance without requiring a full pump replacement.
Q: Can the pump run in either flow direction?
Yes. The flexible impeller design allows the pump to operate in either rotational direction. The direction the shaft rotates determines which port functions as the inlet and which functions as the outlet. Before installation, manually rotate the pump in the intended direction of rotation to orient the flexible impeller blades correctly.
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