Travelling its usual route, or making best speed for Marseilles for some reason?
The typical trade voyage across the Med lasted several months, with stops and waits for favourable winds. If you really were in a hurry, though, you could go flat out. It will still depend on the seasons and luck, but three to four weeks looks eminently doable. (Remind me tomorrow and I can pick out the details, I have a historical atlas sitting on my shelf, just not much time today).