Law 2634, article 29 and article 46 modified by the official gazette no: 19252 reads :
(this is my translation and is far being perfect..)
"the foreigners who enters the country with their yatch can leave their yatch in marinas
certified (authorised) by the ministry of tourism up the two years and can leave the country by another mean of transport...........
The yatches that have been wintered this way in Turkey
and that have been used by their owners at least once every two years can stay in Turkey up to 5 years without any further permit
or whatsoever. The ministry of Tourism is entitled to further extend this duration.........
This regulation is only valid for private boats with no commercial
use of any kind."
Another directive is stating that "the owners, their family
and the crew registered on the boat are entitled for a residence permit
if they have an agreement with a marina. The duration of the residence permit will be in line with the marina agreement an can be max 1 year first time but may be subsequently extended up to 5 years."
Remember, like in almost every country, in Turkey also the legislation regarding these issues is very confusing, sometimes even contradicting. You may hear different answers from different authorities or same authorities in different ports