150 evinrude intruder warning horn.......please help

I am getting a warning horn when running on plan. The horn is very short and "chirpy" and will usually give off a group of blasts when I go over a wake then it will get quiet. Brought it to a local dealer who checked everything out and said it might be a loose connection so the snugged up the screws, charged me and said they would have to water test it if it did not go away. I am trying to figure out what is wrong. The oiltank did ran dry last year perhaps some left over air is still in the oil line?????? VRO???? ANy help PLEASE?????

Make sure the oil tank in full....trace the oil tank sender wires into the motor cover and disconnect them, run the motor, if the chirps are gone replace the oil tank sender.