A hydraulic trailer jack’s power unit affects how quickly it can move a load. Pressure and cylinder size determine hydraulic lifting force; oil flow and cylinder size determine travel speed. Our Primary Mover 12V double-acting power unit uses a 3 HP / 2.2 kW motor. Its motor rating is one part of a system that also includes the pump, valves, battery, cables and jack.
When shopping for a hydraulic trailer jack with a power unit, look beyond the lifting-capacity number. A complete installation needs enough force to raise the trailer, useful operating speed and suitable load control while the leg moves or stays parked. This guide explains what to compare and how our separate power-unit arrangement fits into a trailer build.
Why we offer a 3 HP hydraulic power unit for trailer jacks
Our powered single-jack kit pairs the jack with a separate Primary Mover double-acting hydraulic power unit. The 12V power unit uses a 2.2 kW motor, approximately 3 horsepower, and is also available separately for compatible installations.
Available motor power matters because moving oil against pressure takes power. A properly matched larger motor and pump can supply more oil flow at a given pressure than a lower-powered arrangement. That is the engineering basis for comparing loaded jack speed, rather than judging performance by maximum PSI alone.
The complete power unit determines the result. Pump displacement, motor speed under load, hydraulic efficiency, pressure settings and the electrical supply all affect delivered flow. A motor’s horsepower rating does not, by itself, establish a jack’s cycle time or increase its lifting rating.
View the 12K hydraulic trailer jack kit with power unit , or shop the separate Primary Mover 12V double-acting power unit .
Pressure produces force while flow produces movement
| Specification | What it means for a trailer jack |
|---|---|
| Motor power in HP or kW | The motor’s rated power. Consider it together with the pump, rating conditions and electrical supply. |
| Pressure in PSI | Pressure acting over the cylinder’s effective area creates hydraulic force. A relief setting limits pressure in its circuit. |
| Oil flow in GPM | The volume of oil delivered per minute. At the same cylinder area, more delivered flow means faster movement. |
| Jack lifting rating | The jack’s rated load limit. It is distinct from motor horsepower and from the trailer’s GVWR. |
| Stroke and cycle time | Stroke is travel distance. Cycle time is how long a specified movement takes under stated conditions. |
A smaller motor can still operate a hydraulic pump capable of reaching high pressure. One way to do this is to use a smaller pump displacement, which reduces the oil volume moved per revolution. Two systems can therefore advertise the same maximum pressure while moving the same jack at different speeds.
For example, if one power unit supplies twice the flow of another at the same working pressure, it would move the same cylinder through the same extension distance in approximately half the time, assuming comparable conditions. This is a hydraulic relationship, not a measured performance claim for our kit.
Extension and retraction can also take different amounts of time. The piston rod reduces the effective area on one side of a conventional double-acting cylinder, so the two directions require different oil volumes for the same travel.
Comparing a separate power unit with a compact integrated unit
A compact integrated hydraulic power unit is mounted directly with the jack. A separate power unit connects to the jack through external hoses. Both arrangements can provide powered extension and retraction. Packaging alone does not establish lifting capacity, travel speed or durability.
The separate arrangement gives the installer flexibility in locating the power unit, subject to mounting, hose routing and electrical requirements. On our 12V power unit, choose a dry, weather-protected location with suitable service access. Its separate location also lets you inspect the power unit and jack as individual assemblies.
Compare these details before buying:
- Published motor rating: compare kW or HP with the rating conditions, voltage and duty limits.
- Flow at working pressure: low-pressure or no-load flow does not tell you how much oil reaches the jack while lifting a substantial load.
- Pressure settings: check extension and retraction specifications separately.
- Loaded travel time: compare the same travel distance, supported load and cylinder dimensions, or account for their differences.
- Installation space: include the jack’s complete envelope, hose bends, power-unit mounting space and service access.
- Electrical requirements: match the battery, circuit protection, cables and connections to the selected unit.
A physically larger motor is a useful detail to investigate. The strongest performance evidence is a documented test showing flow or travel time at a stated load and voltage. Until comparable test results are available, choose from verified specifications and the requirements of your installation.
A strong power unit and dual counterbalance valves perform different jobs
The power unit supplies hydraulic flow. The jack’s load-control valves govern oil leaving its cylinder when the load could otherwise drive movement. Increasing motor power does not replace suitable load control.
Our 12K hydraulic jack uses dual counterbalance valves, providing load-control functions for both cylinder sides. They help resist unintended retraction while supporting the trailer and unintended extension while stowed. During commanded movement, they help control outgoing oil and load-driven motion.
Read why dual counterbalance valves matter on hydraulic trailer jacks for a closer look at load holding, controlled lowering and how counterbalance valves differ from basic check valves.
Battery condition and cable installation affect hydraulic performance
A 12V hydraulic power unit depends on voltage delivered at the motor while it is running. A battery may show an acceptable resting voltage but experience substantial voltage drop under load. Loose connections, corrosion and unsuitable cable runs can also reduce the voltage available to the motor.
When diagnosing a slow hydraulic trailer jack, check the electrical supply along with the hydraulic circuit. Follow the power-unit instructions for cable sizing, routing, circuit protection and battery requirements. A larger motor is not a remedy for an undersized electrical installation.
Also check oil level, fluid suitability, temperature, hose restrictions and the installed load-control arrangement. Motor size does not establish a continuous-running duty cycle; follow the operating limits supplied with the unit.
Choose the hydraulic jack package that matches your trailer
| Your setup | Package to consider |
|---|---|
| You need a jack and dedicated power unit | 12K single-jack kit with double-acting power unit . Review the included components and supply the required electrical source. |
| You already have a compatible double-acting power unit | Single-jack Add-On Kit , or a suitable dual-jack package. Add-On Kits do not include a power unit. |
| You have a compatible single-acting dump power unit | Jack-only option plus the matching X-Block hookup kit . Confirm pressure, return connection and hose reach. |
| You need a replacement or separate power unit | Primary Mover 12V double-acting power unit . Match the entire circuit before installation. |
For a shared dump-and-jack system, the hydraulic circuit and controls must suit both functions. A manual selector installation operates one selected function at a time. Use our Jack Kit Selector or contact us to choose the appropriate configuration.
Hydraulic trailer jack power unit questions
Does a 3 HP motor increase a 12K jack’s lifting rating?
No. Our 12K jack retains its 12,000 lb rated lifting capacity. A power-unit change does not increase the jack, mount, frame or trailer ratings. Pressure must remain within the limits of the complete installation.
Can two power units have the same PSI but different lifting speeds?
Yes. Maximum pressure does not specify the oil flow delivered at that pressure. Compare working-pressure flow or measured loaded travel time, accounting for cylinder size and travel distance.
Does double acting mean the power unit has a large motor?
No. Double acting describes powered hydraulic movement in both directions. Motor power is a separate specification.
Can I buy the Primary Mover power unit without the jack?
Yes. We sell the 12V double-acting hydraulic power unit separately . Confirm hydraulic and electrical compatibility before using it in a replacement or custom system.
Can my single-acting dump pump operate this double-acting jack?
A compatible installation can use an X-Block adapter to direct flow to either cylinder side. Read how the X-Block operates a double-acting jack from a single-acting power unit before choosing the hookup kit.
Find the right hydraulic trailer jack and power unit
Browse hydraulic trailer jacks and kits , then compare the complete installation: load rating, mounting dimensions, travel, valve arrangement, power unit and electrical supply. For help, call 985-888-6554 or email sales@primarymover.com with photos of your trailer and existing hydraulic equipment.