45M185A1C20 Hydraulic Motor | Eaton Vickers M Series Vane

Product Overview

The M Series hydraulic motor is Eaton Vickers’ classic high-speed, high-pressure fixed-displacement vane motor, spanning multiple sub-families including 25M, 26M, 35M, 36M, 45M, 46M, 50M, and 51M. These motors offer a choice of 12 torque ratings from 42 to 300 lb-in/100 psi (4.7 to 33.9 Nm/6.9 bar), with displacements ranging from 43.9 to 317 cm³/rev. The series features a unique dual pressure plate design that results in low internal leakage and overall operating efficiencies up to 90%. The motor design can operate at as low as 100 rpm to as high as 3000 rpm at maximum pressures, with the bi-rotational design lending itself to quick reversal motion. They can be stalled at as high as 65% of maximum pressure rating at 1200 rpm without damage.

The 45M185A1C20 (OEM reference 309398-3 / 574889-C) is the 185 lb-in/100 psi torque rating model in the 45M sub-series, with a geometric displacement of 193.2 cm³/rev (11.79 in³/rev), maximum continuous pressure of 155 bar (2250 PSI), maximum intermittent pressure of 172 bar (2500 PSI), maximum speed of 2600-3000 rpm at maximum pressure, and maximum flow of 61.3-61.4 GPM. The 45M185A1C20141 (OEM 574889-C / 309398-3) is the keyed shaft configuration of the same displacement model. The 50M300A1A20114 is the 300 lb-in/100 psi torque rating model in the 50M sub-series, with a geometric displacement of approximately 317 cm³/rev, maximum continuous pressure of 155 bar, maximum speed of 2400 rpm @ 2500 PSI, maximum flow of 100.5 GPM, and maximum output torque of approximately 844 Nm (7470 in-lbs).

The internal rotating parts of the M Series are self-contained in a cartridge kit, making this motor easily field serviceable. In most cases, the motor can stay in place while the ring, rotor, and vanes are replaced with new — cartridge replacement can normally be completed in ten minutes. The motor’s cover can be assembled in four positions with respect to the body. Changing port positions is accomplished by simply rotating the cover, and the cartridge which is pinned to the cover, in 90° increments. The heavy-duty bearing versions (26M/36M/46M/51M) allow for indirect drive options such as gears, belts, and pulleys.

This product is a drop-in interchange replacement for genuine Eaton Vickers M Series hydraulic motors, covering 45M185A1C20 (309398-3), 50M300A1A20114, 45M185A1C20141 (574889-C), 25M65A-1C-20, 35M80A-1C-20, 50M255A-11A-20-143, and other mainstream models. Mounting flange, shaft extension, port configurations, and case drain port location are dimensionally identical to OEM specifications, enabling direct replacement without hydraulic circuit or mounting modification. Every motor is subjected to 100% simulated actual-load testing before shipment, ensuring volumetric efficiency, output torque, and sealing performance meet OEM technical standards.

OEM Part Number Coverage:

• Primary Models: 45M185A1C20 (309398-3), 50M300A1A20114, 45M185A1C20141 (574889-C)

• 25M/26M Series: 25M42A-1C20, 25M42A-11C20, 25M55A-1A-20, 25M65A-1C-20, 26M42A-1C20

• 35M/36M Series: 35M80A-1C-20, 35M95A-1A-20, 35M115A-11C-20, 36M80A-1C20

• 45M/46M Series: 45M130A, 45M155A, 45M185A-1A-20, 46M130A, 46M155A, 46M185A

• 50M/51M Series: 50M220A, 50M255A-11A-20-143, 50M300A-1A20-114, 51M220A, 51M255A, 51M300A

Technical Specifications 

45M185A1C20 (309398-3) Core Specifications:

• Model Code: 45M185A1C20

• OEM Reference: 309398-3 / 574889-C

• Series: Eaton Vickers M Series (45M sub-series, standard bearing version)

• Product Type: High-speed high-pressure fixed-displacement vane motor, bi-rotational, externally drained

• Ring Capacity Torque Rating: 185 lb-in/100 psi (approx. 20.9 Nm/6.9 bar)

• Geometric displacement: 193.2 cm³/rev (11.79 in³/rev)

• Max continuous pressure: 155 bar (2250 PSI)

• Max intermittent pressure: 172 bar (2500 PSI)

• Max speed: 2600-3000 rpm @ max pressure (2600 rpm @ 155 bar, 3000 rpm @ reduced pressure)

• Max continuous flow: 61.3-61.4 GPM (approx. 232 L/min)

• Max continuous torque: Approx. 361.6 Nm (3200 lb-in) @ max pressure

• Theoretical torque: 20.9 Nm/6.9 bar

• Overall efficiency: Up to 90% (varies with motor size, pressure, speed, and fluid viscosity and temperature)

• Control type: Fixed displacement, balanced vane design

• Mounting flange: SAE C 2-bolt

• Shaft type: 1-1/4 inch 14-tooth splined (standard), 1-1/4 inch keyed (optional), 5/16 inch key

• Port connections: SAE 4-bolt flange

• Rotation: Bi-rotational

• Seal material: Buna-N (NBR) standard

• Bearings: Standard bearings

• Weight: Approx. 39 kg (85 lb)

50M300A1A20114 Core Specifications:

• Model Code: 50M300A1A20114

• Series: 50M sub-series (SAE D flange version)

• Product Type: High-speed high-pressure fixed-displacement vane motor, bi-rotational, externally drained

• Torque Rating: 300 lb-in/100 psi (approx. 33.9 Nm/6.9 bar)

• Geometric displacement: Approx. 317 cm³/rev

• Max continuous pressure: 155 bar (2250 PSI)

• Max intermittent pressure: 172 bar (2500 PSI)

• Max speed: 2400 rpm @ 2500 PSI

• Max flow: 100.5 GPM

• Max output torque: Approx. 844 Nm (7470 in-lbs) @ max pressure

• Mounting flange: SAE D 2-bolt

• Shaft type: 1-3/4 inch 13-tooth splined (standard), 1-3/4 inch keyed (optional), 7/16 inch key

• Special Options: 114 (50M series special feature code)

• Weight: Approx. 73 kg (160 lb)

45M185A1C20141 Reference Specifications:

• Model Code: 45M185A1C20141

• OEM Reference: 574889-C / 309398-3

• Geometric displacement: 193.2 cm³/rev (11.79 in³/rev)

• Torque rating: 185 lb-in/100 psi

• Mounting flange: SAE C 2-bolt

• Shaft type: 1-1/4 inch keyed shaft (Code 1)

• Special Features: 141

M Series Full Model Displacement & Torque Reference:

• 25M/26M Series: Torque ratings 42/55/65 lb-in/100 psi; Displacements 43.9/57.7/68.7 cm³/rev; Max speed 3600–4000 rpm; Flange SAE B 2-bolt

• 35M/36M Series: Torque ratings 80/95/115 lb-in/100 psi; Displacements 83.6/100.3/121.9 cm³/rev; Flange SAE C 2-bolt

• 45M/46M Series: Torque ratings 130/155/185 lb-in/100 psi; Displacements 138.0/163.2/193.2 cm³/rev; Max speed 2600–4000 rpm; Flange SAE C 2-bolt

• 50M/51M Series: Torque ratings 220/255/300 lb-in/100 psi; Displacements approx. 276/297/317 cm³/rev; Max speed 2200–3200 rpm; Flange SAE D 2-bolt

Model Code Breakdown (Example: 45M185A1C20):

• 45M: Product series, 45M indicates the 45M series, 45 is the ring size, M stands for motor

• 185: Ring capacity torque rating code, 185 lb-in/100 psi

• A: Mounting flange and port connections code (A = SAE 2-bolt mounting flange and SAE 4-bolt flange connection)

• 1: Shaft type code (1 = Straight keyed, 11 = Splined)

• C: Cover position code (C = Port connections in line)

• 20: Design number

Key Technical Advantages

1. Dual Pressure Plate Design with High Operating Efficiency
The M Series features a unique dual pressure plate design that results in low internal leakage and overall operating efficiencies up to 90%. The pressure plates, rotor, and cam ring are made of hardened high alloy steels, while the cast iron port plate and end cap are chemically etched to offer a fine crystalline surface allowing better lubrication at start-up. The motors start out with high efficiencies and operate at those levels throughout the life of the motor — inherent in this vane motor design. Double-lip vanes reduce sensitivity to fluid pollution.

2. Fast Serviceability with Cartridge Interchangeability
The internal rotating parts of the M Series are self-contained in a cartridge kit, making this motor easily field serviceable. In most cases, the motor can stay in place while the ring, rotor, and vanes are replaced with new — cartridge replacement can normally be completed in ten minutes. The torque capability of motors within the same model series can be changed by changing the cartridge or cam ring. Port orientation adjustments can also be done in the field — the cover can be rotated in 90° increments to change port positions.

3. High Speed, High Pressure Combined Performance with Quick Reversal Capability
The M Series operates at continuous pressures up to 155 bar and intermittent pressures up to 172 bar, with speeds from 100 rpm to 3000 rpm at maximum pressures and up to 4000 rpm at reduced pressures. The bi-rotational design lends itself to quick reversal motion. They can be stalled at as high as 65% of maximum pressure rating at 1200 rpm without damage. Because both ports can be pressurized at the same time, the M Series is perfect for multiple motors connected in series.

4. Hydraulically Balanced Design with Low Wear and Long Life
The 25M-50M series motors are hydraulically balanced to reduce wear and heat-producing friction. All internal inlet chambers are equally and diametrically opposed. As a result, pressure induced radial loads are balanced. Shaft bearings only have to carry external loads so wear is greatly reduced. The heavy-duty bearing versions (26M/36M/46M/51M) allow for indirect drive options such as gears, belts, and pulleys. For more than two decades, the reliability of these high performance motors has been field proven on a variety of machinery applications.

Application Areas

• Construction Machinery (Core Application): Excavator swing drive, loader travel drive, crane swing mechanism, road roller drum drive

• Mining Equipment: Mine winch drive, drill feed mechanism, crusher drive

• Marine & Offshore: Deck winch drive, anchor windlass drive, steering gear drive

• Industrial Equipment: Mixer drive, shredder drive, compressor drive, generator drive, test bench drive

• Material Handling: Conveyor drive drum, heavy-duty forklift drive, stacker drive

• Agricultural Machinery: Combine harvester drive, large tractor hydraulic drive

• Special Applications: Elevator scraper drives, hydrostatic drives, auxiliary applications

Expert Maintenance Tips

Pre-Installation Preparation:
Clean all ports and mounting flanges with lint-free wipes or clean compressed air before installation. Verify O-ring integrity. The 45M185A1C20 uses an SAE C 2-bolt flange, while the 50M300A1A20114 uses an SAE D 2-bolt flange — confirm the flange specification matches the system before installation. Torque mounting bolts in a diagonal sequence over 2–3 passes. After installation, manually rotate the output shaft to confirm free and smooth rotation without binding.

Drain Port Management:
The M Series is an externally drained motor — the case drain port must be connected to a drain line routed separately back to the reservoir with the end submerged below the oil level. Drain line back pressure must not exceed 2 bar; excessive back pressure will damage the shaft seal. For multi-motor series connections, ensure proper case pressure distribution.

Hydraulic Fluid Management:
Use anti-wear hydraulic oil with ISO VG 46 or ISO VG 68 viscosity grade (corresponding to the 70 SUS recommended viscosity). Maintain fluid cleanliness at ISO 18/16/13 or NAS Class 8 minimum. Operating temperature should not exceed 80°C. Internal parts are lubricated by the operating fluid itself; therefore, preventive maintenance is limited to keeping the fluid clean and maintaining an acceptable viscosity range. System filters should be replaced frequently.

Cartridge Service and Replacement:
The cam ring, rotor, and vanes of the M Series are self-contained in a cartridge kit. When performance restoration is required, the cartridge can be replaced directly without disassembling the entire motor. The drive cartridge is accessible by removing the motor’s cover and can normally be replaced in ten minutes without removing the motor from the machine. When installing a new cartridge, verify all vanes are properly seated and spring preload is uniform. Cartridge kits are recommended for spare parts — they are assembled and tested before shipment.

Port Position Adjustment:
The M Series motor’s cover can be assembled in four positions with respect to the body. Changing port positions is accomplished by simply rotating the cover, and the cartridge which is pinned to the cover, in 90° increments. Ensure the O-ring between the cover and body remains intact during adjustment.

Periodic Inspection:
Check volumetric efficiency every 500 operating hours or quarterly. Test method: lock the output shaft at rated pressure and measure leakage flow. If leakage exceeds 10% of rated flow, internal wear has entered an accelerated phase — schedule service or replacement. Also inspect shaft seals for seepage and bearings for abnormal noise or vibration.