It is hard to hear on your video but if it is that constant cricket-like sound throughout the video it is probably the temperature alarm. If it does it on startup with the engine completely cool then there is something wrong with the sensor (mounted on top of the engine near plugs), the wiring or the beeper itself. Since yours does not sound normal it may be a defective beeper. But first check that the pisser in back of the ski is streaming water when you are accelerating and there are no blockages in your jet pump or cooling flow to engine. You can also test the sensor with an ohmmeter to see if it is grounding the tab where the wire connects when you hear the alarm. If it is then feel the engine to see if it is hot. The shop manual probably has a test for the sensor. It is supposed to close at a certain temperature (I think around 205 degrees F).
