If you put the fishfinder into standby mode, it stops transmitting. It's very easy to tell especially with a boat out of the water because the audible clicking sound stops.
Everything else on the MFD will function normally so you can update software and manage settings. If you shut the MFD down with the fishfinder transmit off, it will start uo with it in standby.
My small boat is kept on a trailer in the winter and I have done this many times to protect the transducer from overheating elements while making changes to the MFD settings or updating, which can happen without any water on it to cool the surface.