Do any of the new depth finders show depth and maps at high speeds using the transducer that comes with them? I have an old Hummingbird 797 si and it loses depth at high speeds and I read where I need another thru the hull transducer and a Y cable to do that with any SI depth finder. I was thinking about getting an Elite Ti totalscan but was not sure if it read depth at high speeds in addition to slow speed side imaging etc.

All Structure scan is lost above 20MPH. Sonar depends on the installation of the transducer.
If most sonar transducer are mounted properly, they will keep sonar at hi-speed.

Mapping isn't in the transducer. It is internal and via chart card & GPS. Losing depth while running at high speed is not uncommon for most all models. On some occasions, it is possible to obtain depth while running at high speeds. One can obtain the in hull transducer and "Y" cable to achieve depth reading at high speeds or you can simply follow a good Chart system that will show you what depth you are running in and what is ahead.