In general you'll find that most motor yachts up to 50' or so will have a draft of under 4'. Up to about 80' it's about 5' to 6'. Above that 7' to 11' until you get real big and above 80' (and often below) you'll generally find them carrying a dink or tender which will allow the yacht to anchor out and still come in. So draft isn't usually as important as prudence.
In reality Scotty's area is much harder to navigate as lakes will often have old 20' trees sticking up from the bottom of 21' deep lakes after the spring thaws and rains. Getting local knowledge there is key as it is when transiting questionable areas anywhere in the world. When in doubt follow someone bigger than you or put out a call for local knowledge. Otherwise dead slow.