We took chartplotters from Garmin (top left), Furuno (top right) and Raymarine (bottom) and used their respective black box conversion kits to add sounder capabilities.

Do you multi-task? There’s a new breed of fishfinder that will allow your existing chartplotter or radar display to multi-task. This new technology allows boaters with limited electronics installation space to add a full-featured fishfinder to their navigational system without adding another electronics display.

It’s one of the hottest new gadgets in the marine electronics market. Three of the major manufacturers now offer them—Garmin, Furuno and Raymarine.

What We Tested

All three manufacturers agreed to send us their version of the sounder conversion kit. Garmin sent us its GSD 20 sounder module, Raymarine sent its DSM250 digital sounder module and the Furuno shipped us its FF1 Network sounder. …