There was no direct passage >from South Africa to Boston!!! A passenger going >from South Africa to Boston would have probably travelled to England on a Union Castle Liner then transferred to another ship >from one of the ports in England to America. You will have to look at all the arrivals >from England. You might try looking at the Poor Jews Temporary Shelter Database first if your passenger travelled within the dates of 1896 - 1915.
Also, look at the the South African InfoFile on JewishGen for more info.