Hello-
Spraying is very common in unneutered domestic cats, but is even more common in F1 bengals and savannahs since they are so close to the wild ancestor. Although most f1's are sterile, there are the OCCASIONAL ones that are not, so if you have not had this boy sterlized, that would be first on the list, unless you are planning on breeding.
This boy isn't going to behave like a fully domesticated feline, and I believe this is something you may have to continue dealing with. Some suggestions that MAY help-making certain all feline members are spayed/neutered. Invest in several feliway plugins. These put out soothing phermones in the home that often counteract severe hosers like this guy. Finally, if absolutely nothing changes, talk with your vet. There are some medications such as buspar, that can be prescribed for a short time that may help the situation. With hybrid cats, spraying is one of the possible negative behaviors you may have to deal with. I think savannahs are the ultimate in nifty cats and I hope you are successful at stoping this soon.
Please let me know if I can help further.
Feline Healthcare
16 yrs health care mgmt & issues relating to cats, reproductive issues and multicat environments