Autopilots also interact with other onboard electronics, such as plotters and fish finders, often via NMEA 2000 networks. How you can program that interaction depends on the abilities of your other equipment.
If you own a newer Raymarine fish finder, you can pause its screen - if you see structure or fish as you're under way - put the cursor on the object and mark it as a waypoint. You then tell the Smartpilot to take you back to that location.
If you navigate to a known wreck or pinnacle already stored as a waypoint, you simply dial in a pattern once you're there. If you select a spiral, your boat will work around that waypoint in ever-larger circles.
On the West Coast, tuna fishermen frequently use box patterns once they find a school. "If you get a blind 'jig' (lure) strike, the first thing you do is make a box a mile or half-mile square around the spot to stay near the school," says Ron Ballanti, a Simrad spokesman.
When Stotesbury sight-fishes striped marlin, he uses boxes or circles to keep his boat near the numbers - which often mark a pinnacle where upwellings and bait occur - so he can glass the seas with binoculars. "It takes only seconds to program" he says. "Really, it's very user-friendly."
Straight and Narrow
Sometimes Stotesbury simply needs to navigate a straight course in dim light so he can be sure to bypass navigational buoys and the tips of islands. Both Simrad and Furuno units offer autopilot modes that lock onto a virtual waypoint past the horizon. Furuno calls this function "advanced auto," while Simrad calls it "no drift."
Without that function, an autopilot compensates for set and drift by constantly readjusting the heading, but it can't eliminate drift. Furuno's advanced-auto mode keeps the vessel smack-dab on the Course Over Ground line.