running 16v on lowrance

Yes, but what you will be doing in return for lower current in the supply wires is to overdrive the internal regulator inside the Lowrance unit that drops the voltage down to the motherboard & screen operating voltage of 5.5 V. (Common sense and Physics says that there is no way that, when measured with a laboratory instrument, that the screen would shine brighter. 5.5 V is 5.5 V.) Also, take care to disconnect the unit from the battery whenever on charge as the charge voltage for the 16 V battery is 17.75 V which exceeds Lowrance Maximum Voltage Range of operation.(3.55 V per cel × 5 cells)
 
Yes. I feed my units with a 16v converter off my 36v 110ah lithium trolling motor battery. Averages about 15.9-16.2v all day. Garmin 1222 LVS34plus, Lowrance HDS12 and Lowrance HDS9