Common sense dictates that autopilot can free you up to do all manner of other enjoyable chores besides steering. Rigging baits, navigating, trimming sails and, of course, keeping a watch out for other vessels at all times. Nothing can beat the convenience of a working autopilot. But what to do when your pilot stops working correctly?

An autopilot is a difficult instrument to install (only a single sideband with its peculiar grounding requirements may be harder) — not something an average do-it-yourselfer wants to undertake. In fact, most autopilot manufacturers agree that more problems arise from poor installations than any other source.

Once you have an autopilot problem, however, you can often trouble-shoot it yourself since the various components making up the instrument are few in number and straight forward in function.

Don't mistake what an autopilot does. It steers a boat in a straight line in a wide variety of sea and wind conditions. An autopilot doesn't correct for a boat that steers poorly without an autopilot. Such boats have other problems that need to be addressed before you consider adding an autopilot. So always remember the first step in troubleshooting an autopilot; if your autopilot worked perfectly at one time and now doesn't, the problem can be found in one of the electronic components. If it has never worked properly, the problem may be with the boat itself.

Boat Problems

If you can't steer a straight course manually, (flat-bottom boats have a particularly hard time with this) then an autopilot won't do it either. Twin-screw vessels with two different props (different pitch, diameter or cupping) will also be hard to steer straight as one prop exerts more torque than the other. An autopilot will not correct this nor be able to perform acceptably. If your rudder(s) is bent or has been mounted incorrectly (toed-in for example) then the steering will be squirrely and impossible for your autopilot to compensate. If you tighten one stuffing box more than the other on a twin-screw boat, the tendency will be for the boat to pull to one side. Other factors that can lead to poor steering performance are too much weight on one side of the boat, trim tabs adjusted unevenly and even a large concave area on a hull from sitting on a cradle incorrectly blocked for winter storage.

Barring inherent boat problems, here are some places to look for determining a problem with the autopilot itself.

The Electronic Compass

The majority of autopilot problems stem from the electronic (or fluxgate) compass that gives all-important heading information to the autopilot. Treat it with care just as you would a normal magnetic compass. It should always be mounted in a place unaffected by surrounding metal, electrical wiring or other electronics. One boat had a microwave oven directly above the fluxgate. The magnetron in the microwave disrupted the compass reading every time the oven turned on.

The Pump

It takes muscle to turn engines or rudders and the hydraulic pump must be sized correctly for your boat's size and speed. Don't fall for the trap of buying a small pump because it's less expensive. If it can't turn your boat then the system is useless.

Obviously, the faster the boat, the less rudder movement is required for turning so fast boats may not need as big a pump. If you primarily use your boat for trolling for fish, you may want to consider a slightly larger pump since keeping a straight course at low speeds takes more muscle. Also, nearshore cruisers need less pump capacity than true offshore vessels do as larger seas and stronger winds require a stronger You can often tell if you have a problem by measuring the power the pump uses. If it reads more than factory specifications, you have a problem. Often air in the hydraulic system (assuming you have hydraulic steering and not mechanical) will cause the pump to work too hard.

The Microprocessor

If your boat averages the correct course but seems to turn too far in each direction to accomplish it, the "sea state" adjustment is probably the culprit. The brain of the autopilot has a "deadband" of space on either side of a desired heading that sets its limits — usually 1 to 5 degrees. This means the unit will wait until your vessel has gone off course by this amount before making a correction. The wider the deadband, the less work the pilot does and the less power it uses.

Rudder Feedback Sensor

The rudder feedback sensor tells the autopilot which direction the rudder or drive unit is facing. If this is out of adjustment, the autopilot will think it is driving a straight course when, in fact, the boat is turning. Being a computer, the unit will not be able to function within this dichotomy.


Today's autopilots usually get hooked up to a GPS or chart plotter that feeds heading information to the pilot. Certainly life gets easier when you can place your cursor on a series of waypoints, then push go and have the autopilot steer you to each waypoint in turn — automatically. However, if the GPS stops giving heading information, your course won't change once you reach your first waypoint. The autopilot will simply read the heading information from the flux gate compass and continue on its last known heading. Chances are good that an alarm will go off when you lose position information from the GPS, though.

Interfacing needs a common language for the autopilot and other electronics to communicate with each other. The most common language (or protocol) is NMEA 0183 (National Marine Electronics Association). While this is an industry standard, all that is needed for communication to go awry is a misplaced comma or a letter or number transposed in the software program. Good technicians can now compare the protocols for two different instruments and determine if this has caused the problem.


If the wiring for the system is too small, the system won't function optimally. Make sure your installation uses factory-specified wiring.

The Software

Finally, the software in the microprocessor that makes it all work can simply be wrong for your boat. According to John Cinis of Navico, "Industry-wide, today's autopilots will work perfectly for over 95 percent of the boats out there. But some of the other 5 percent can pose insurmountable idiosynchracies that can't be resolved for that particular boat. They might need a different utopilot to work correctly."

Don't let this article scare you away from autopilots. An overwhelming majority of these units get installed perfectly and work flawlessly. You can't imagine the freedom an autopilot provides until you try one. I'd never own a boat without one again.

Autopilot Manufacturers

676 Island Pond Rd.
Manchester, NH 03109-5420
(603) 647-7530

271 Harbor Way
South San Francisco, CA 94083
(415) 873-9393

Metal Marine Pilot
2119 Mildred St. W.
Tacoma, WA 98466
(253) 564-5902

676 Island Pond Rd.
Manchester, NH 03109-5420
(603) 647-7530