1 year old male wants to bite 2 year old female?

We just got him a short time ago and don't know his background except that he was found in the engine of a car. Our female cat who is spayed is very well behaved but the new male who is neutered won't leave her alone even though she has established herself as the dominant one. He's very hyper and chases her everywhere and then tries to mount her and bite her. We have a spray waterbottle that we use to get him to stop and it works temporarily but before you know it he's back for more. Is there anything else that we could try - I have a gut feeling that he was a feral cat who had to fend for himself. We give him lots of love and attention and sometimes he is very good but still has the crazies, especially at night. He finds it difficult to relax although he does finally settle down later at night.