Reading depth at high speed

I have a HB 998Csi in the dash of my PIV. There is a “puck” mounted in the bilge and the side imaging ducer on the jack plate; connected with a Y cable. I consistently lose depth readout above about 30 mph; regardless of water conditions. As the lake is currently low, finding the bottom is more of an issue. I also have a Vexler FL-10 flasher installed. Would this unit be better to find the bottom at high speeds?Are there some settings I can use on the HB to improve performance?Is the Vexler hard to use?Thank Youjwt