The readout boxes can be turned off in the full screen SI view only...(water temp and depth will be overlayed in the bottom left of the screen)...
I think the setting to turn off "SI Readouts" is under the "Sonar" tab in the main menu...
(You might think about adding your opinion about the readout boxes in an email to HB ...it's been on the wish list for a LONG time now)...
Rickie