Guide · Autopilot commissioning
Tuning Rudder Gain on a Marine Autopilot
If the boat snakes back and forth across the course, the pilot is likely working too hard. Rudder gain is the first adjustment to check — and the sea state changes how much gain the boat needs.
See what rudder gain does to the track.
Pick the sea state, then change the gain one or two clicks at a time. On Simrad pilots each click moves the setting 0.05 from a 0.50 default. The dashed line is the course you asked the pilot to steer; the bright wake is what the boat actually does. Rough water usually needs a click or two more gain than calm water.
Sea state
In calm water the 0.40-0.60 range usually settles the track.
Rudder gain
0.80
Each click moves 0.05. Simrad pilots default to 0.50.
Recommended next move
Lower rudder gain one or two clicks, run the boat, then reassess.
Gain
0.80
Off course
0 ft
Response
Aggressive
What rudder gain changes
Rudder gain controls how much rudder the pilot applies for a heading error. More gain makes the pilot react harder; less gain softens the correction. On Simrad pilots the setting moves in 0.05 steps from a 0.50 default, so each click is a small, deliberate change. Sea state, speed, loading and trim can all change the way the same setting feels.
Gain too high
The boat fishtails
The pilot applies too much rudder, crosses the desired course, then throws rudder the other way. The stern keeps swinging and the track becomes a repeating S-shape. A boat that wanders slowly off course and is slow to come back is usually showing the early side of the same problem — it is under-correcting where a balanced setting would hold the line.
Lower rudder gain one or two clicks (0.05 per click). Run the boat and watch. Keep the setting if the track improves.
Sea state
Rough seas need more gain
In calm water the boat responds quickly, so a moderate setting holds the track. In rough seas the same setting can leave the boat sluggish and slow to come back, because wind and sea keep pushing the bow off the course. Expect to run one or two clicks more gain in rough water than you did in calm — and expect to back it off again when it flattens out.
Tune for the conditions you are running in. One or two clicks at a time, and re-check when the sea state changes.
A careful on-water tuning sequence
- 1Choose open water, steady speed and safe conditions with a qualified person keeping watch.
- 2Engage the autopilot on a steady course and observe several correction cycles before touching the setting.
- 3Change rudder gain one or two clicks (0.05 per click on Simrad) in the direction the symptom calls for.
- 4Let the boat settle and assess the full track. Make a second click only if the same symptom remains.
- 5Repeat at the normal working speed and loading. Save or record the setting that gives the cleanest track.
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