3100 SERIES SAILING INSTRUMENTS. Navman's new generation of instruments are the cutting edge of digital marine technology: they feature the advanced NavBus system, which allows complete freedom to build the system you want by using any combination of displays with only one set of transducers. Visibility is fantastic with up to 38mm backlit digits and nighttime use is easy with amber lighting and backlit keys. The 3100 series instruments are extremely simple to use and to connect. They now offer greater flexibility to meet your boating needs. SPEED: Features all the essential functions such as speed, distance, temperature and time, plus some exciting extras, such as the Trim speed function. Speed range: 0-50 knots/0-58 mph/0-93 km/h. Trip and sum logs auto range to 19,999 units. Displays speed in knots, MPH or KPH.