There is no On / Off switch for the Sea Ray Navigator's GPS.
The brain of the GPS on Type 1 Sea Ray Navigators is in the Power Supply box.
This is a long black box with some connections on one end.
The GPS antenna is connected by the white coaxial cable.
With the Sea Ray Navigator powered off, feel in the back of that Power Supply box, there is a rocker switch (power). Turn in off, give it a few seconds, then back on .
This may help reset the connection between the computer and GPS.