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Marine Autopilot

Below-deck system · Garmin

Garmin Reactor 40

Garmin's whole-of-fleet autopilot with Shadow Drive and a nine-axis attitude sensor.

Indicative price
$2,900–$5,200 unit
Fitted
$4,200–$8,500
Rated for
Sized by drive or pump
Editor score
83 / 100
HydraulicMechanical wheel (cable, chain or rod)Steer-by-wire / joystickOutboard (cable or hydraulic)Fishing and trailer boatsPower cruisingCoastal cruisingOffshore / bluewater

Reactor 40 is the course computer at the centre of every Garmin autopilot, sold in packs that match the steering system: Hydraulic (with a 1.2 or 2.0 litre pump), Compact Hydraulic for small boats, Mechanical/Retrofit/Solenoid (paired with a linear or from Garmin's partners), and Steer-by-wire for Yamaha Helm Master, Volvo Penta, Mercury, Suzuki and SeaStar Optimus systems. The same core, with a Garmin wind sensor and a suitable drive, becomes a sailboat autopilot.

Two things distinguish it. The first is the nine-axis (attitude and heading reference system) that keeps heading stable while the boat pitches and rolls, so it holds a course through a chop that has cheaper pilots wandering. The second is on hydraulic packs: turn the wheel and the pilot disengages automatically; leave it alone for a moment and it re-engages. For a fishing boat where the skipper is constantly nudging the helm, it is the single most-praised autopilot feature in Australia.

Control is through the GHC 50 head or any GPSMAP chartplotter; a wireless GHC 20-style remote is optional. For sailors the wind steering is competent rather than special, and the sail-specific features lag B&G and Raymarine. For the power fleet, particularly boats already running Garmin GPSMAP and sonar, it is the obvious pick.

Verdict

The best autopilot for most Australian power boats, and the obvious choice if you already run Garmin. Sailors with wheel or tiller boats should compare it with the Raymarine EV-200 and B&G NAC-3 before deciding.

Garmin Reactor 40 (Hydraulic, Mechanical, Steer-by-wire and Sail) drive sizing

Sized by steering system. Hydraulic packs: 1.2 L pump for cylinders to roughly 200 cc, 2.0 L pump for larger; Compact Hydraulic for small single-cylinder outboard boats. Mechanical packs depend on the third-party drive chosen; sailing yachts to roughly 10–20 tonnes depending on drive.

Specifications

Autopilot components, voltage and steering modes

Sensor
Reactor 40 course computer with integrated nine-axis AHRS; can be mounted below deck
Control
GHC 50 helm control, GPSMAP chartplotter, optional wireless remote
Drives
1.2 L or 2.0 L hydraulic pump, Compact pump, third-party linear/rotary drives, or steer-by-wire integration
Shadow Drive
Hydraulic sensor that disengages the pilot when the wheel is turned by hand
Voltage
12 V DC (most packs); 24 V on selected pumps and drives
Network
NMEA 2000, Garmin Marine Network via GPSMAP
Power draw
1.5 A typical, 10 A peak. Pump draws only while correcting. Averaged consumption on a planing boat at cruise is typically 1–2 A.
Steering systems
Hydraulic; Mechanical wheel (cable, chain or rod); Steer-by-wire / joystick; Outboard (cable or hydraulic)

Modes

  • Heading hold
  • Route following from GPSMAP
  • Wind hold (with Garmin wind sensor)
  • Pattern steering: zigzag, circle, cloverleaf, u-turn
  • Heading step and dodge

Features

  • Shadow Drive automatic disengage and re-engage on hydraulic packs
  • Nine-axis AHRS attitude stabilisation
  • Full integration with GPSMAP plotters, autopilot page and alarms
  • Steer-by-wire packs for joystick-equipped outboard and IPS boats
  • Pattern steering for fishing

For and against

Autopilot strengths and limitations

Strengths
  • Shadow Drive changes how you use an autopilot on a fishing boat
  • Excellent heading stability in short chop
  • Seamless with a Garmin plotter and sonar network
  • Strong national dealer presence through tackle, marine and 4WD electronics outlets
Limitations
  • Sailing features are competent but behind B&G and Raymarine
  • Sail installations rely on third-party drives, which adds a supplier
  • GHC 50 head is small for a big wheelhouse; many owners drive it from the plotter

Who fits it

Boats and places where this system is recommended

Boat types

Australian waters

  • New South Wales → The Hunter and South Coast game-fishing fleet's choice on hydraulic outboard boats.
  • Queensland → Shadow Drive for the plate-alloy sportsfisher fleet from the Gold Coast to Cairns.
  • Western Australia → For the plate-alloy offshore fishing fleet on hydraulic outboards.
  • Northern Territory → For the aluminium fishing fleet on hydraulic outboards.
  • Newcastle, Lake Macquarie and Port Stephens → The obvious fit on a flybridge cruiser out of Newcastle or Nelson Bay. Shadow Drive means you can steer around an anchored bulk carrier without hunting for the standby button, and it comes back on course when you let go.
  • Brisbane and Moreton Bay → The most common upgrade on bay power boats with hydraulic steering. Shadow Drive suits bay work where you are constantly nudging around crab pots, bait schools and the Port of Brisbane channel.
  • Gold Coast and Tweed → The default upgrade or replacement on Gold Coast hydraulic power boats. Shadow Drive is made for water this busy: take the wheel to avoid a PWC, let go, and the pilot picks the course back up.
  • Whitsundays and Mackay → The pick for a Mackay-based power boat running out to the reef. Shadow Drive suits water where you are constantly dodging pot floats, and the pack handles the hydraulics on most local sportfish boats.
  • Cairns and Far North Queensland → A practical fit on a mid-size hydraulic sportfish or flybridge boat out of Cairns or Port Douglas. Shadow Drive matters in reef country, where you alter course for coral, bait and boats constantly.

Questions

Garmin Reactor 40 (Hydraulic, Mechanical, Steer-by-wire and Sail): frequently asked

What is Shadow Drive and does it work with outboards?

Shadow Drive is a hydraulic sensor plumbed into the steering line. When you turn the wheel it disengages the autopilot; when you stop, it re-engages after a short pause. It works on any compatible hydraulic system, including hydraulic outboard steering, but not on cable-steered outboards.

Can the Reactor 40 steer a sailing yacht?

Yes, with a mechanical pack and a suitable linear or rotary drive, plus a Garmin wind sensor for wind steering. It holds a course well. Owners who want sophisticated sailing modes, gust response and racing features are better served by B&G.

Do I need a rudder feedback sensor?

Not on Garmin hydraulic packs, which are designed to work without one. Mechanical packs with linear drives generally use one. Garmin's dealer documentation lists the requirement per pack.

Alternatives to consider

The systems most often weighed against this one.

Other below-deck system systems

Head to head

Comparisons featuring this system

ProductsRaymarine EV-100 vs Garmin Reactor 40 →For a sailing yacht under 7.5 tonnes, the EV-100 wins on sailing behaviour, pack completeness and price. For any hydraulically steered…ConceptHydraulic vs linear drive →Hydraulic steering gets a hydraulic pump; there is no sensible alternative. A yacht with mechanical steering and an accessible rudder stock…ProductsNavPilot 300 vs Reactor 40 →Boats with Garmin plotters and sonar should buy the Reactor 40; the integration is worth it and Shadow Drive is excellent. Heavy twin- and…ProductsGarmin SmartDrive vs Reactor 40 Retrofit Options →Retain a drive only when condition and supported integration are documented. Compare SmartDrive as a complete new installation when the…ProductsRaymarine EV-150 Power vs Garmin Reactor 40 Hydraulic →Choose on a supported hydraulic configuration and the controls you need aboard. A compatible existing chartplotter may influence the…
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Autopilot commissioning and operator training

A $8,500 installation with no handover is a gamble. Half a day on the water with the installer or an instructor covers the modes, the override, the alarms and a failure drill. It is the cheapest safety equipment aboard.

Find an instructorOpen the competency checklist