I also have 17' PS and the start up beep is really loud. My boat has the same loud beep every time I turn on the key and when I start the boat with the push button. I went into the settings and shut off the shallow water depth alarm, low fuel warning and zero off alarms, but that did not stop it. Not sure if this has anything to do with it, but my boat seems to start hard and I easily loose 3-5 volts during start up. Maybe that is a low voltage alarm?
I guess I get the idiot beep!!