This is one of the best fish finders from Humminbird with monochromatic display. Apart from that it has quite a multitude of features which can make it quite a reliable unit.
The Hummingbird Fish Finder 581i Combo is endowed with a high-resolution 16 lvl grayscale display, 5-inch wide, 640 x 320 pixel resolution. Since this unit has a FTSN LCD display, it requires less power to operate and it’s obviously cheaper.
It’s equipped with DualBeam sonar, 200kHz / 20° and 83 kHz / 60°, with a reliability down to 800 ft depths. Has a 2000 Watts PtP power output. Even if it’s not a SI Hummingbird Fish Finder and also lacks the DI technology, the normal sonar still does its job, allowing you to see what passes beneath the boat, identifying the shape of the bottom, measuring depth and locating the fish you’re looking for.
For a black-and-white fish finding device this unit has plenty of GPS features, which needless to say, increase its utility. The 581i Combo is Navionics compatible, has the UniMap built-in cartography system, which covers the U.S. coastal line and most of the in-land lakes and rivers, with a 30 meter / pixel resolution. It also has a 50 channels Internal GPS, making it a nice and reliable navigational unit.
As far as it concerns the Hummingbird 581i Combo memory, it has the same card as the Best Hummingbird Fish Finders. You can write in its memory up to 3,000 waypoints, 50 tracks (20,000 points each) and 50 routes.