The Dardanelles are the narrowest straights you can’t just pass them, you need to book passage and you cant just sail into the Sea of Marmara with your AIS turned off, in fact you can’t enter Turkish waters with it turned off and you will get boarded.
The US has a much larger coast line and even then you usually have to communicate with someone if you don’t want to get a visit from the coast guard.
Also I haven’t seen a single luxury yacht you can rent without a crew, this isn’t any different than chartering a private jet you get a pilot, co-pilot and a flight attendant as part of the package. A yacht isn’t a small boat you need a proper captain, an engineer and a service crew.
A boat that can sail form anywhere in the med to Russia needs to be quite big and have quite a bit of fuel and supplies.
This doesn’t seem to be an operation that can be executed so simply you need to make sure there is enough fuel/supplies which may raise flags on shore when you book it, you need to find a way to deal with the crew, you need to be able to replace the AIS and have a valid ship registration to pass through the Dardanelles into the Black Sea.
While I’m sure an organized crime cartel might be able to pull this off but the resources and planning this job would require would be quite insane.