Autopilot Anchor Mode: What It Does

What anchor mode does

Anchor mode is a feature on some marine autopilots that helps you stay within a set area while anchored. Instead of holding a fixed heading, the autopilot uses its heading sensor and GPS position to detect when the boat drifts. It then adjusts the helm to bring the boat back toward the center of the watch circle you define.

This is useful when wind, current, or tide push the boat while you are anchored. Without anchor mode, you would need to adjust the helm manually or reset the anchor. With it, the autopilot does the work, letting you focus on other tasks or rest.

Anchor mode is not the same as a heading hold or route following. It is designed for a stationary situation, not for moving along a course. The autopilot keeps the boat within a radius you choose, rather than steering a straight line.

How anchor mode works

Anchor mode relies on two main inputs: the heading sensor and a GPS position source. The heading sensor tells the autopilot which way the bow points. The GPS provides the boat's position over the ground. By comparing the two, the autopilot can tell if the boat is swinging on the anchor or dragging.

When the boat drifts beyond the watch circle, the autopilot applies rudder to steer back toward the center. It does not try to hold a compass heading; it tries to hold a position. This means the boat may swing with the wind or current, but it stays within the circle you set.

The size of the watch circle is usually set by you, either on the control head or through a connected chartplotter. A smaller circle keeps the boat tighter, but may cause more frequent corrections. A larger circle gives more room, but the boat may drift farther before the autopilot reacts.

Checking if your autopilot has anchor mode

Not all autopilots include anchor mode. It is more common on newer models with advanced control heads and GPS integration. To find out if your autopilot supports it, check the control head's feature list on the maker's page. Look for terms like "anchor," "watch circle," or "position hold."

On this site, the catalogue lists the control head in the box for each pack. If the control head is a basic model, it may not have anchor mode. If the pack includes a more advanced head, such as one with a color display, anchor mode is more likely. For example, the Furuno NavPilot 300 includes a gesture controller and advanced modes.

You can also check the autopilot's manual or the maker's website for a list of modes. The manual will tell you if anchor mode is available and how to set it up. If you are unsure, contact the maker or a dealer with your model number.

Anchor mode vs. anchor alarm

Anchor mode is different from an anchor alarm. An anchor alarm is a simple alert that sounds when the boat moves beyond a set distance from the anchor. It does not steer the boat; it only warns you. Many chartplotters and GPS units have anchor alarms built in.

Anchor mode actively steers the boat to stay within the circle. It is a more advanced feature that requires the autopilot to be engaged. An anchor alarm is a passive safety net that works even when the autopilot is off.

Some autopilots with anchor mode also have an anchor alarm function. If your autopilot does not have anchor mode, you can still use an anchor alarm on a chartplotter or a separate device to alert you to dragging.

What to look for in a listing

When reading an autopilot listing, look for the control head model and the feature list. The control head is the part you use to select modes. If the listing mentions "anchor mode" or "watch circle," that is a clear sign the autopilot supports it.

If the listing does not mention anchor mode, check the control head's name. Some control heads, like the Raymarine p70 series, are basic and may not have anchor mode. Others, like the GHC 50 or Furuno NavPilot 300, have more features. You can compare control head options in the control head guide.

The catalogue on this site lists the control head in the box for each pack. You can compare the control head names across listings to see which ones are more advanced. If you are unsure, the maker's page for that control head will list its modes.

Anchor mode and your boat type

Anchor mode is available on both sail and power autopilots, but it is more common on powerboat models. This is because powerboats often anchor for fishing or swimming, where holding position is useful. Sailboats may anchor less often, but anchor mode can still be helpful.

For a fishing boat, anchor mode is a valuable feature. It lets you stay over a reef or wreck without constantly adjusting the helm. Some autopilots even have specialized modes for fishing, like Furuno's FishHunter mode, which can perform maneuvers around a target. See the fishing boat guide for more.

For a cruising sailboat, anchor mode can reduce the workload when anchored in a current. It is not a replacement for a proper anchor watch, but it can help you stay put. Always keep a lookout and use an anchor alarm as a backup.

Anchor mode and NMEA 2000

Anchor mode often requires a GPS position source, which is usually connected via NMEA 2000. NMEA 2000 is a standard for marine electronics that lets devices share data, including position and heading. The autopilot uses this data to know where the boat is and where it needs to go.

If your autopilot does not have a built-in GPS, it needs to receive position data from a chartplotter or GPS antenna over NMEA 2000. The NMEA 2000 standard is described on the NMEA page as a low-cost, moderate capacity network for interconnecting marine electronics.

When choosing an autopilot with anchor mode, check that it has NMEA 2000 connectivity. This is usually listed in the specifications. If the autopilot has NMEA 2000, it can receive GPS data from a compatible source. Learn more in the NMEA 2000 guide.

Anchor mode and safety

Anchor mode is a convenience, but it does not replace a proper anchor watch. The U.S. Coast Guard Boating Safety page emphasizes the importance of boating safety education and responsible operation. Always keep a lookout for other boats, hazards, and changes in weather.

Anchor mode can help you stay in position, but it cannot prevent all dragging. If the anchor does not hold, the autopilot will try to steer back, but it may not be able to overcome the drag. Use an anchor alarm and check your position regularly.

The autopilot is a tool, not a substitute for seamanship. You are responsible for the safety of your boat and crew. Anchor mode can make anchoring easier, but you should always be ready to take manual control.

What to pick for your situation

Questions

Does every autopilot have anchor mode?

No. Anchor mode is a feature on some autopilots, usually those with advanced control heads and GPS integration. Check the control head's feature list on the maker's page.

Can I use anchor mode without a GPS?

Anchor mode needs a GPS position source to know where the boat is. If your autopilot does not have a built-in GPS, it must receive position data over NMEA 2000 from a chartplotter or GPS antenna.

Is anchor mode the same as an anchor alarm?

No. Anchor mode actively steers the boat to stay within a watch circle. An anchor alarm only sounds an alert when the boat moves beyond a set distance. You can use both together.

How do I set the watch circle size?

The watch circle size is set on the control head or through a connected chartplotter. The manual for your autopilot will explain how to adjust it.

Does anchor mode work on all boat types?

Anchor mode is available on both sail and power autopilots, but it is more common on powerboat models. Check the specifications for your autopilot to see if it supports anchor mode.