My radar displays all contacts reverse. How do I get the display reversed? model #1731

I agree with Nico-Fixus, the heading alignment is one of the things to be checked. Unless this is a new installation it is unlikely that the Radome (antenna) got removed and reinstalled facing the wrong way. So antenna orientation would not be a concern.

I have seen units that for some reason the wrong Radome was selected in the configuration of the Navnet display.

Read the model number on the Antenna, then check that correct antenna type in loaded in your display.

The problem is you have never set your heading alignment or your radar is on backwards. Check your installation guide for radar heading alignment procedures. Now it shows up as a 1732 which is a navnet. but you say it's a 1731 which is different.
On the 1732 navnet power on the device while holding the menu button. this will take you into installation mode. Next wait for the radar to stop counting down. next transmit the radar. press menu>system config>installation setup>radar setup > next page. your heading alignment adjustment will be there. adjust 180 degrees and you should be good. Just line it up with a bouy after wards.

On a 1731, I think you have to hold the gain button down on startup and then it should open the option for the installation menu to come up. check page 6-17 in you operators manual to see how to do it. if you don't have the manual you can obtain a pdf from www.furunousa.com click on search in the upper right hand corner and type 1731 then select 1731 then goto manuals. Cheers!