Leaving in Istanbul
I also dream of the tour of Black Sea and made quite a bit of search... There are beatiful places to see in turkish coast, Sochi, Yalta, Sevastapol and Odessa. Two problems:
1-Ucraine and Russia
doesn't seem to be yatch freindly. Plenty of burocrocy, paperwork, expense and most of the time head
2-The season is very short.. Beginning of June through September. Even the end of September can be risky. Althought being an inland sea, Black sea is known with its strong winds and breaking waves..
Since the prevailing winds are northeaterlies, the best way should be start from Istanbul
towards Bulgaria. (Clock wise turn)
Unpleasant strong southerlies are common in spring and automn but are very rare in summer and not very strong anyway.
In summer you can expect relatively quite sea, with winds from north/north east up to 15-20 nm. Sea water
at this time of the year is about 19-22 C, the wheather beetween 22-30 C in the day and 12-18 C in the night.
I am ot sure if KAYRA stil being organised. That's the best way of touring Black Sea and rather safely..