I have yet to hear of the 1.5 thing but considering a 788 is not one of the new units they are producing that sound very odd. All new units are the 9 series rather than the 8 series. I had a 788 I did get rid of though because interference made the speed and depth jump all over the screen. Only unit I ever had this problem with. All of the 8 series birds read in tenths starting at .1 as I have a 998.