I have a 2010 188vx ranger with 175 opti that has the 2 inch square mercmonitor, question is can i change to the round mercmonitor eco 4.602 by just plugging it up with the harness currently hooked to the square one. Boat also has nmea network but it doesn't appear to be hooked to the motor. only thing that comes up on the garmin when hooked to it is lowrance precision gps and temp sensor.What would it take to hook nmea to motor.