ABT TRAC hydraulic bow and stern thrusters

Hydraulic thrusters are what ABT TRAC is built around. The company started in 1986 as Arcturus Marine Systems, moved to the TRAC gearbox design with dual 5-blade counter-rotating props in 1993, and today sells hydraulic thrusters from 8 to 28-inch tunnels. If you've been aboard a big trawler with stabilizers and a bow thruster that just keeps pushing, there's a fair chance it was this kind of system.

Why hydraulic at all

A DC thruster's limit is heat in the motor. Run it long enough and it shuts down to protect itself. A hydraulic thruster has a small motor at the tunnel and the power comes from an engine-driven pump, so it can keep running as long as the hydraulic system can supply flow and shed heat. For boats that hold position in current, dock in big wind, or carry heavy windage, that's the whole argument. Our electric vs hydraulic thrusters comparison goes deeper.

The range

ABT TRAC lists seven hydraulic sizes. Its current spec sheets give maximum horsepower rather than a single thrust figure:

Instead of a boat-length range, each size has a windage chart: vessel side area in square feet against wind speed, with premium, average and marginal performance bands. On the 10-inch, for example, the chart runs from 350 to 1,600 sq ft of windage; on the 24-inch it runs from 1,750 to 9,250 sq ft. That's how a thruster should be sized on a big boat, since length tells you little about how much wind a tall superstructure catches.

The spec sheets also list tunnel options in fiberglass, aluminium or steel for each size, with outside diameters and weight per foot. A 20-inch steel tunnel is listed at 110 lb per foot, which tells you something about the scale of these installs.

Build

ABT TRAC's design points:

• High-efficiency piston motors. Piston motors generally hold efficiency better under load than gear motors, at higher cost.
• Twin counter-rotating propellers on every size.
• Oversized gears and bearings, on purpose.
• Propeller hubs that shroud the gearbox to protect the prop shaft.
• A rotating seal guard protecting the shaft seals from line and debris.

Control is single-speed or proportional. On larger systems, TRAC Link ties thrusters, stabilizers, windlasses and selected hydraulic loads into one CAN bus network with touch-screen panels, and ABT TRAC says it monitors hydraulic pressure and stabilizer performance too.

The hydraulic system is the real install

ABT TRAC says most of its hydraulic thrusters run from a TRAC integrated hydraulic system, which can also power stabilizers, windlasses, capstans and cranes. In practice, a hydraulic thruster install includes:

1. Engine-driven pump(s), and often an electric backup pump for docking with engines idling.
2. Reservoir, filtration and cooling sized for the combined loads.
3. Valves and manifolds, often pre-built as a hydraulic power unit. ABT TRAC has offered custom HPU fabrication since 2007.
4. Hose or hard-line runs to the bow (and stern), routed and supported properly.
5. The tunnel and thruster, then controls and commissioning.

On new builds this is planned from the start. As a refit, it's a big job, and it makes most sense when stabilizers are being added at the same time. Our bow thruster installation and stern thruster installation pages cover the tunnel side.

Downsides worth saying out loud

• Complexity. Hoses, fittings, pumps and coolers all need maintenance. A leak in the forepeak is a real possibility over the boat's life.
• Weight and space. The pump, reservoir and lines add up, even if the thruster at the tunnel is compact.
• No simple thrust number. Comparing an ABT TRAC hydraulic unit with a European DC unit by kgf isn't possible from the public sheets; you compare by windage chart and horsepower instead.
• Engine dependence. Without an electric backup pump, the thruster depends on the engine being up and the PTO engaged.

Questions to settle before ordering

• What else runs on the hydraulics? Stabilizers, windlass, davit or crane all compete for flow. The pump and cooling have to handle the realistic combined load, not just the thruster.
• Do you need to thrust with engines off or at idle? If so, plan an electric pump or generator-driven supply.
• Bow only, or bow and stern? ABT TRAC's control panels come in single or dual configuration, and adding a stern unit later means more plumbing aft.
• Which tunnel material? ABT TRAC lists fiberglass, aluminium and steel tunnels for each size; match it to the hull.

Alternatives

If there are no hydraulics aboard, start with ABT TRAC's DC thrusters for the 8 to 12-inch sizes, or its AC versions, which use a variable frequency drive for speed control and to limit motor inrush current on generator-equipped yachts. For boats that need a hydraulic retractable instead of a tunnel, see Max Power's R-series and Quick's BTRH; ABT TRAC's own history notes it shipped its first ReTRAC retractable in 2013, so ask the factory what's current.

Verdict

For a trawler or large yacht that already runs hydraulic stabilizers, an ABT TRAC hydraulic thruster on the same system is hard to argue with: unlimited-feeling run time, heavy-duty hardware and one control network. For anything smaller or simpler, it's more system than the boat needs. If you're planning stabilizers and a thruster together, talk to us early, before anyone sizes the pump.

Questions people ask