All of the screens were easy to see in direct sunlight. It was under cover where we saw major differences in screen quality. From right to left: the Garmin GPSMAP 168 Sounder, the Garmin GPSMAP 188 Sounder, and the Lowrance LMS-320DF.

Type the words “combo unit” into a Google Internet search and you’ll come up with 127,000 responses. For sale: TV-VCR combo units, fax-printer combo units, washer-dryer combo units, even cell phones that can take digital photographs. Now more than ever, people want to kill two birds with one stone. Boaters too.

A single piece of electronics that merges two or more functions not only saves space at the helm but also can improve the usefulness of the product. We’re thinking of electronic chartplotters with radar overlays, or split screens that display the contours of the bottom on the right and your heading on a chart on the left. …