How to calibrate a B&G or Raymarine autopilot: workshop procedure

By Pol Conin — Skysat, marine electronics workshop in Carnac, Brittany. Published October 3, 2026.

Before you open a menu

Commissioning will not fix a badly placed compass or a bent linkage.

• Software and network. Raymarine requires every component to run current software. On B&G systems, data source selection is required at first start-up and whenever anything on the NMEA 2000 network is replaced.
• Compass. Navico wants the Precision-9 at least 2 m from the engine, away from ignition cables and large metal objects, “particularly the autopilot drive unit”, close to the waterline and never upside down. Raymarine puts the EV-1 at least 1 m from any source of magnetic interference, electrical cables included, level within 5°, arrow pointing at the bow.
• Rudder sensor. For an RF25N: sensor centred in line with the rudder stock, lever on the centre mark, 1:1 linkage, then the helm put hard over both ways while you check that nothing binds. Navico warns that ignoring the alignment marks can trigger a rudder feedback alarm.

B&G NAC-2/NAC-3: dockside commissioning

The NAC-2 (drives up to 8 A continuous) or the NAC-3 (30 A) is set up from a Zeus or Vulcan chartplotter, or from a Triton² fitted with the Triton² pilot keypad (Autopilot menu, Installation).

1. Boat type. Sail (the other options are Displacement and Planing), then length and cruising speed. With Sail selected, Virtual Rudder Feedback (VRF) is not available: you need a physical sensor, an RF25N on the network or, on a NAC-3, an RF300 with frequency output.
2. Drive. Reversible motor (pump, linear drive) or solenoids; 12 or 24 V to match the drive, since B&G warns that the wrong voltage can damage both drive and computer; clutch output if the drive has one; rudder deadband on Auto.
3. Rudder feedback. Select the source, then follow the guided calibration, which establishes the sensor's direction. The zero found here gets corrected at sea.
4. Rudder test. It checks drive direction, finds the minimum power needed and caps rudder speed. The rudder should make a small movement within 10 seconds, then travel both ways; if not, you get an alarm.

On an H5000 Pilot computer, commissioning is done from the H5000 pilot controller, with a three-point rudder calibration: starboard hard over, port hard over, midships. Confirm the displayed angles even if you do not change them: B&G says this is what keeps the rudder off the end stops. The rudder test then caps rudder speed at 8°/s.

B&G: the sea trial

Calm sea, open water, well clear of traffic: that is what the NAC manual demands.

1. Compass. The Precision-9 ships with auto calibration set to Auto: it learns while you sail and phases in new parameters over about 20 minutes. To calibrate on demand, set auto calibration to Off, select Calibrate in the device list (the autopilot setup guide also takes you there), then turn through about 390° at 2 to 3° per second.
2. Offsets. Heading: take the charted bearing to a visible object and line the bow up on it. Pitch and roll: alongside, boat in normal trim.
3. Rudder zero. In calm conditions, find the rudder angle at which the boat runs straight, then use Set rudder zero.
4. Check. In AUTO, the pilot should hold within ±1° on average in calm sea and wind. Make course changes of 10 to 20°, then 60 to 90°, both ways.
5. Autotune if course keeping disappoints. Between 5 and 10 knots, the pilot runs S-turns for about 3 minutes and sets rudder gain and counter rudder, then drops back to Standby: you are steering again.
6. Fine tuning. Gain too high: overshoot and unstable steering; too low: slow return to course. Overshoot at the end of a turn: more counter rudder; sluggish, creeping response: less. Autotrim sets how quickly a constant offset (weather helm, current) is trimmed out.

Raymarine Evolution: the Dockside wizard

The EV-1 is both the 9-axis heading sensor and the course computer; the ACU, from the ACU-100 to the ACU-400, powers the drive. Raymarine sets the order, from a p70s or p70Rs controller: hull type, Dockside wizard, hard-over time if there is no rudder reference, compass linearization, compass lock if needed.

1. Vessel hull type (Vessel Settings): Sail, Sail (Slow turn) or Sail Catamaran. Raymarine presents these as guidance only and asks you to favour a safe, dependable steering response.
2. Dockside wizard (Commissioning menu, in Standby), starting with drive type: Type 1/2 linear, Type 2/3 hydraulic linear, Type 1/2/3 hydraulic pump, wheel drive, tiller…
3. Align rudder, only with an M81105 rudder reference: centre, hard to port, hard to starboard, centre. This sets the limits.
4. Rudder limit. 30° by default without a rudder reference, taken from the alignment with one. Raymarine recommends about 5° less than the maximum rudder angle.
5. Drive check. Centre the rudder and let go. With a rudder reference, the pilot moves it to port then starboard by itself; without one, you confirm each side. Answer “no” to both and the wizard exits: check the steering.

Without a rudder reference, measure the hard-over time: rudder hard to port in Standby, engage Auto, alter the locked heading by 90°, time the rudder movement to estimate full port to full starboard, then refine it in use. In that case, Raymarine warns, the installation itself must stop the steering from hitting the end stops. Raymarine highly recommends the M81105 (it is essential with an ACU-300), and Evolution ignores any rudder sensor not wired directly to the ACU.

Raymarine: linearization and response level

Evolution has no rudder gain, no counter rudder, no AutoLearn and no manual compass calibration. You still have to turn the boat.

1. Linearization. It starts by itself after about 100° of turn between 3 and 15 knots and needs at least 270° to complete; a full 360° speeds it up. It pauses below 3 knots, above 15, when the rate of turn is too slow, or under heavy magnetic interference (pontoons, metal hulls, underwater cables). Raymarine support suggests 15 to 20 minutes of large figure-eights at a slow rate of turn.
2. Deviation (Diagnostics, About Pilot). The manual says to move the EV-1 from 45°; Raymarine support from 15°, aiming for under 5° on a GRP boat.
3. Heading offset. Compare against a reliable reference on several headings, then use Compass Offset (±10°). A 2 to 3° offset is common when the EV-1 could not be aligned with the centreline. GPS COG is only a valid reference with no current and no leeway.
4. Compass lock. Compass Lock freezes the linearization. Release it before a long passage: the earth's magnetic field changes from one area to another.
5. Response. Leisure for long passages where tight course keeping is not critical, Cruising for good course keeping without overworking the system, Performance for tight heading control. With a rudder reference, if the pilot hunts, raise Rudder Damping one level at a time and keep the lowest acceptable value.

When to recalibrate

Limits and pitfalls

• Compass deviation. An error that changes with heading cannot be tuned out with gain or counter rudder. Raymarine's list of culprits: steel screws and tools, the engine block, speakers, pumps, electric motors, high-current wiring. B&G adds the toolbox or anchor stowed next to the compass. On a Triton², above 30% local field, find the metal or move the compass; above 100%, calibration fails.
• Badly zeroed rudder sensor. A boat that pulls to one side, alarms: on Evolution, NO RUDDER REFERENCE when the sensor leaves its 50° operating range, and among the causes of DRIVE STOPPED, a sensor that does not reflect the end stops. Fix the mechanics before the electronic zero.
• Gain too high in a seaway. Overshoot and unstable steering according to the NAC manual, plus lost speed according to the H5000 manual. More counter rudder also means more rudder activity on a straight course in big waves.
• Race settings on a cruising boat. Plenty of sailors think they want high gain everywhere; B&G's product director points out that it is not that simple. When cruising, start from the Autotune values or the Cruising level, and change one parameter at a time.
• Limits of this guide. Menus change between software versions (Raymarine manual for v3.13, NAC manual from 2020): the documentation shipped with your equipment takes precedence.

Workshop verdict

• New B&G install on a sailboat (NAC-3, Precision-9 and RF25N pack): follow the manual's order, no shortcuts. Calibrate the compass before any Autotune: without a calibrated compass and log, B&G says, tuning the pilot is meaningless.
• Evolution without a rudder reference, on a passage-making boat: fit the M81105. Otherwise end-stop protection rests on the mechanical installation and a stopwatch estimate of hard-over time.
• Evolution deviation above 15°, or a Precision-9 calibration that fails: move the sensor: beyond these thresholds, no setting makes up for a poor location.
• Partial refit: redo the step tied to the part you changed, then a check at sea. Never the dockside part alone.
• No calm day in sight: wait, the NAC manual requires calm seas for the trial. Or hand commissioning over to the workshop.

Sources

• Navico, NAC-2/NAC-3 Commissioning Manual, 988-11233-003 (2020).
• Navico, Precision-9 Installation Guide, 988-10984-004 (2023).
• Navico, RF25N Rudder Feedback instructions, 988-10277-001.
• B&G, H5000 Installation Manual (988-10635-002) and Triton2 Operator Manual.
• B&G, product pages for the NAC-3, NAC-2 and Precision-9.
• B&G, blog posts Autopilots: Key Calibration and Settings and Understanding Performance Functions.
• Raymarine, Evolution EV-1/ACU Installation Instructions, 87180 Rev 7 (07-2024).
• Raymarine, p70/p70s/p70R/p70Rs Commissioning & Operation Instructions, 81402 Rev 6 (11-2025).
• Raymarine support: Setup Evolution Autopilot (May 2025).

Further reading

• B&G or Raymarine autopilot on a 40-50 ft sailboat
• Electronic compass: fluxgate, gyro or attitude sensor
• Upgrading an autopilot: the pre-refit audit
• Hydraulic or electromechanical drive unit

Disclosure: Skysat distributes B&G, Navico and Raymarine. This article was neither sponsored nor reviewed by the brands mentioned.