Can't say, since it depends on speed and desired comfort, stop-offs, etc. We purposely spread that part of our last trip over 3 actual travel days (with sightseeing breaks in between): Myrtle Beach to Georgetown
, Georgetown to McClellanville, McC to Charleston. From memory, each of those legs was between 4-6 hours, mostly at about 8 kts except for Charleston Harbor.
You can actually go faster for much of it if you like, so you can do your math depending on target speeds...