My DS is 8, and we have had similar battles. They may well be too young for homework at this age, but you get stuck in a cycle - the school want them to do it, they don't want to be the only one not handing it in, but at the same time, they don't want to do it. I'm not sure on the benefits of homework at this age, but I'm not prepared to make my children deal with the effects of my stance when they are the ones at school.
My DS is a little better now, though he still has his moments. I don't take any crying or moaning, or any stamping at all. They don't do that at school when a teacher asks them to work. He's doing it at home because he knows he can get away with it - it works! Anything like that is met with a 10 minute spell in his room, but it is made clear that he will be back to complete homework. We also tie good behaviour in with bedtimes - so if he had a huge tantrum and slammed his door that night, he would be going to bed at the early bedtime, not the late.
What has been most successful for us is tying it in with what he wants. Which is computer time. Be it Xbox, PC or whatever. DS loves Minecraft, and always hopes to have time on it after school. He gets some time, once his homework is done (if he has any), and it works like this:
Hypothetical example: he has one piece of homework that should take no more than 15 minutes. He starts at 4pm. He is told that he should complete his homework (and neatly - though this may take more time, it's taken us about 6 months to get to this point), and then it is computer time until 5pm. If he finishes his homework in 15 minutes, he gets 45 minutes on the computer. If he whines and procrastinates, and it takes him 50 minutes, then he gets 10 minutes on the computer. Computer time is over at 5pm. Not finishing homework by 5pm means no screen time for that day. Rinse and repeat the next day.
It is HARD to find a balance. I don't want him to hate homework, but at the same time I don't want him to think he can have a strop and get out of doing it because I'm a soft touch. Our strategy works with us, though it has taken time (we also have a treat box on a Fri for good behaviour all week), because we are strict with it, consistent, and we do monitor the homework - if something is just too tough, we take a different approach.
If you are getting nowhere with him and nothing works, simply tell him that you aren't spending hours moaning at him. The 4-5pm thing works because it's limited time - who wants to spend hours over homework? Tell him you will write a note to the teacher saying he refused to do it. Homework shouldn't be taking over your life.