Seriously, get the kid checked for hyperactivity. It ruined my life. Do not let it ruin his.
My son is eight and he does this too. And when he’s not talking, he’s singing or making little sound effects. He even goes on talking when he’s playing by himself in his room, which is pretty funny. I like to listen outside his door because the child is having such a good time in there!
Get him to write more; it could help him to slow down to ‘pen speed’ and think a bit more about what he’s saying, but it’s generally a good thing anyway; don’t dam the stream, divert it somewhere productive.
Now, let me ask you, is a lot of this chatter inane questions that he expects answers to? That’s the worst!
My youngest sister (still 4 years older than me) is a rapid chatterbox to this very day. She also talks with her hands. I discovered years ago that if I want her to slow down when she’s talking to me, I just have to grab her hands and hold them still.
Works like a charm.
The ‘holding hands’ idea is a good one, but not exactly effective when he is two rows behind me in my truck. I’d have to be ElastaGirl which would rock.
His two best friends ( of an ever circling number of best friends) are the quiet types.
I do tell him to “rest his mouth” and “Breath a little” and “Let X get a word in edgewise.” but really, he has some kind of sheild around him and just blah blah blah blah…
I’ll give his teacher a few weeks to get use to him and see if she notices any problems.
As a kid and early teen, I was constantly accused of not telling my mother important things like when I had a field trip or if I was spending a night at a friend’s house. It was never actually that I didn’t tell her, it was that she had learned how to tune out my constant stream of chatter, and therefore missed the one true Important Thing amidst the barrage of inconsequential crap. By my sophomore year in high school, I learned to just write it down and let her deal. Wasn’t my fault she didn’t listen. 
I still talk a lot, and I also have a tendency to talk with my hands. mrklutz’s solution works on me, as well.
One thing I will say- I was (and still am at times- I’m working on it) a constant chatterer. Some of the most hurtful things I’ve ever heard said to me are “Shut up” and “will you just stop talking already!!” and the like. As a kid you don’t realize you’re doing it, or maybe you’re just having a good day and are excited and it’s very easy for an adult to make the child feel unimportant and hurt with expressions like that. Not saying you do those things, just a fair warning.
One thing that helped me (as an adult, anyway) was being taught the concept of listening and asking open ended questions of others. It sounds simple, but it opened up a whole new world for me. Instead of filling silence with nervous chatter about nothing, I learned to say “tell me about your hobbies” or “tell me about the last movie you saw” and the like. I found that over time I enjoyed listening more then I liked talking. It takes self awareness that I"m not sure a child that age possesses, but what could it hurt to try?
When jr starts babbling, encourage him instead to ask his father/whoever is in the room at the time a question and practice listening to the answer and paying attention. Also, it helped me a lot to be involved in on stage productions as an outlet for that energy- school plays and the like.
His teacher might really appreciate a phone call or visit now, rather than waiting (if you’ve never met his teacher).
I’m a teacher, and how I handle issues like this really depends on what I know about a situation. If I don’t know anything, sometimes I can be harsher than I need to be.
I’m guessing this is more than just a talkative kid. From what you’ve written, it sounds pretty severe.
It also sounds like you have a sense of humor and his best interets at heart…and that you are very honest about him!
Sitting in the car sends my son into witter mode, and on one looooong road trip, finally my patience shattered. We were just heading into what I knew was a very long tunnel, so I yelled “You are to be SILENT while we are in the tunnel!!!”
Instant silence (he knew he’d gone too far!)
The tunnel was long, and I forgot that I had yelled, just enjoying the peace.
As the car came out of the tunnel, the sunlight hit the windscreen, and he started talking, right from the very sentence he’d been cut off from! It was like rain hitting the windscreen. Ahhhh!
The first thing that comes to mind in this situation is you should enroll this kid in every literature, poetry, and foreign language course you can get your hands on. He might get sick of words, or failing that, at least learn how to use them well.
I have THREE chatterboxes, only now, instead of being chatted at all at once, they take turns calling. Hallgirl 1 is in Philadelphia and calls daily, Hallgirl 2 is in Minot and calls about every three days, and Hallboy is still at home and chatters all the time. Actually, with the girls gone, it’s very quiet (even with Hallboy home), and man, do I miss the chatter.
I have to admit, when they were teens and chatty, I knew what they were thinking, and what was happening, and all that comes along with being a teen.
Enjoy the chattering while you can, and for crying out loud, NEVER tell him to shut up.
Wearing black turtlenecks and asking people if they’d like to touch his monkey?
Two of my brothers and I are the same way when it comes to talking, in that once we get on an academic subject, that we know a lot about, we will talk endlessly. If I start talking about the Civil War, it’s hard to get me to shut up. My mother just tunes us out.
About telling the child to shut up, it depends on the child, and how sensitive they are. My nephews talk nonstop. My sister’ll try to be patient, but everyone has their limits, and she will tell them to shut up. And they will, for a good 5-10 minutes, and it’ll start up again, like nothing happened. But it’s a good 10 minutes of silence.
I saw an interesting suggestion for this problem the other day - put him on the phone when the telemarketers call. He gets to talk, and you don’t have to listen. 
My mother is a non-stop talker, to the point that I can only spend a couple of days with them before I start going bonkers, and I often let the answering machine pick up when I see her number on the caller ID.
Our 14yo daughter is VERY quiet. She was very loud as an infant, when she had evening bouts of colic, but that was over by the time she was four or five months old.
Our 10yo son was such a QUIET baby. He never cried to speak of–I even had to remind him every few hours that he was supposed to eat, and he never complained about diapers. He started sleeping through the night when he was about two weeks old, and we patted ourselves on the back, quite sure that a quite baby was our just reward for the colicky baby we had the first time around. Then we found out that he was completely deaf for all practical purposes, and that was the main reason he was so quiet. A couple of surgeries later, his hearing was good enough for hearing aids to help, but by that point he was already a year old and WAY behind on verbal language development.
Now, though he is VERY loud. Not only does he talk non-stop about meaningless stuff given every opportunity, but he often interrupts other conversations to do so. In addition, his speech is far from perfect. He almost stutters, he stops mid-phrase for long moments while he tries to think of the next word, he garbles many sounds, and it is REALLY hard to understand exactly what he is trying to say, much less follow his train of thought when he really gets going. He also has ADHD, and borderline Asperger’s Syndrome.
We set model examples of how conversations should take place. We remind him quite frequently about turn-taking, and staying on topic, and focusing on enunciating his words. He has been getting speech therapy since he was an infant, both for sounds, and for the tonality, and for social behavior.
Nothing has helped significantly yet. His ADHD meds do help somewhat during the day, but he is at school most of that time. By the time he gets home, the meds have worn off, and it’s like he has to get caught up on the backwash of thoughts that the meds were keeping dammed up all day. 
This sounds EXACTLY like my son!!!
We do actually sometimes tell him to shut up, but only after we have tried everything else we can thing of, or if there is so much else going on at the time that we just don’t have any more patience to spare. It doesn’t seem to phase him in the least, although I always feel guilty when it happens.
We did actually try this once a couple of years ago. I don’t think it had any effect on our son, except that it gave him another topic of conversation for the next week or so.
In moments of Orange Level Chatter, I like to dial up my FIL and then go to my son with the handheld and say, " Here, talk to Opa." and then I have personal silence for a good 30 minutes.
I am going to talk to the teacher in the morning. I see her every day anyways.
I forgot to mention this- I don’t know how well it will work on a child, but I took up knitting and crochet about 2 years ago and EVERYONE comments about how quiet it is when I’m working on a project. I simply can’t engage my brain in that focused activity and babble at the same time. I can chat and listen, but it really breaks that stream of conciousness chatter habit. Maturity has helped me learn to be still, but taking up a hobby that uses both hands and a focused concentration has really done the trick- like magic.
7 years old is a great age to learn either skill, by the way, and the new trend in knitting (in all the magazines and such) is that it’s cool to be a male who knits, so who knows- it could work!
<------ Wiping iced tea from nostrils. That was deeply hilarious. A warning next time would be much appreciated…