Installation · 7 minute read
Marine autopilot calibration
Commission a marine autopilot through dockside checks, compass calibration and sea trials. Verify drive direction, rudder limits and steering response.
A new autopilot is not finished when the last cable is connected. Commissioning is where the computer learns the boat, the rudder limits are set so the drive cannot destroy the steering, and the compass is calibrated so the heading it holds is real. Skipping it, or letting a busy installer skip it, is why so many pilots wander, hunt or throw alarms in their first season.
The process is the same across brands: dockside checks, a compass calibration circle, a flat-water tune, then a sea-trial in real conditions. Done well it takes half a day. Done with the owner aboard it doubles as the first lesson.
Key facts
- Dockside
- Drive direction, rudder limits, rudder reference alignment
- Compass
- Slow circles on flat water until deviation is accepted
- Flat water
- Auto mode, small course changes, check for overshoot
- Seaway
- Response settings, wind mode, following-sea behaviour
- Record
- Write the settings down and keep them aboard
Dockside rudder limits and drive-direction checks
Check the supply voltage at the course computer. Confirm the network sees the sensor, the head and any plotter. Set the vessel type in the head's setup menu (sail, power planing, power displacement) because it changes the default tuning. Then run the drive: with the rudder amidships, command a turn and confirm the rudder moves the right way. If it turns the wrong way, the drive or the reference is reversed in the menu.
Set the rudder limits so the drive stops short of the mechanical stops; over-travel is how linear drives bend tiller arms and hydraulic pumps overload. Align the rudder reference so its centre matches the rudder's centre and its travel is symmetrical. Modern systems walk you through these steps on the head.
- Vessel type set correctly
- Drive direction confirmed
- Rudder limits inside the mechanical stops
- Rudder reference centred and parallel
- Network shows every device
- Supply voltage within spec with the drive working
Compass calibration
Every magnetic heading sensor needs to learn the boat's own magnetic field. The head prompts a calibration: motor in slow, steady circles on flat water, usually two or three turns at around two minutes per circle, until the system reports deviation is within tolerance. Raymarine's Evolution does much of this automatically in the background as you sail; Garmin, B&G and Furuno run a defined routine. If deviation is high, the sensor is too close to something magnetic and must be moved.
Then check heading against a known transit or the plotter's course over ground on a calm day with no tide. A few degrees of offset is normal and corrected in the menu.
Flat-water tuning
Engage Auto on flat water at cruising speed. Change course by ten degrees and watch: the boat should settle on the new heading with at most one small overshoot. If it oscillates, gain is too high. If it settles slowly and wanders, gain is too low. Adjust rudder gain and in small steps and repeat. Adaptive systems narrow this down for you but still benefit from a check.
Sea trial in real conditions
The pilot that is perfect on flat water is not tuned. Take the boat out in a moderate seaway and try every mode you will use: Auto on a reach and a run, Wind mode upwind and downwind, Track on a short route with a tide. Adjust response until the boat holds a course without the drive working constantly. Note the settings for each condition. On a sailing yacht, set (Raymarine) or (B&G) if fitted, and try the tack and gybe functions with the crew ready.
Do the sea trial with the owner aboard
Record autopilot calibration and trial results
Every setting, by condition, on a laminated card at the nav station: vessel type, gain, rudder gain, , response, wind mode, rudder limits, the alarms and their values. When the head is replaced or the settings reset after a software update, the card saves the boat a second sea trial.
Questions
Frequently asked
How long does autopilot commissioning take?
Half a day for a straightforward system, including a short sea trial. Complex systems with multiple stations or a satellite compass take longer.
Can I calibrate the compass myself?
Yes. The head walks you through it. Choose flat water, no tide, a calm day, and keep the turns slow and steady.
Why does my pilot overshoot every course change?
Gain too high or counter rudder too low. Reduce gain a step, retest, then adjust counter rudder.
Does the sea trial need rough weather?
Moderate conditions are enough to tune response. Test the following-sea behaviour when you get the chance, in daylight, with the settings card handy.
More in installation
Practise autopilot operation with an instructor
Habits are learned at the helm with someone watching. The training section explains what a good instructor covers and where to find one in your state.