Help on serial port

Trying to find information on ther serial spec was not easy but it is 4800,8N1 with no flow control.

Try a slightly different sketch an see if it works. You will need to alter the serial monitor baud rate to 4800

void setup(){
  Serial.begin(4800);
  Serial3.begin(4800);
  delay(1000);
  Serial.println("Setup Complete.");
}

void loop(){
  while (Serial3.available()){
    Serial.write(Serial3.read());
    delay(1);
  }
  while (Serial.available()){
    Serial3.write(Serial.read());
    delay(1);
  }
}