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