How do I let the guy I have been talking to that I am no longer interested?

If you’ve only been talking, then you shouldn’t find it all that hard to just tell him you aren’t interested in the way he might be. The way I’ve handled people who text too much or those I’m not really interested in talking with very much is to delay answering. Don’t just jump back with an answer. Delay for longer and longer periods. He’ll get the message. You are under no obligation to try to date him if he doesn’t appeal to you. Personally, I think the best thing to do is tell him as nicely as possible that he’s not your type. He might not like it, but that’s how relationships work—we win some and we lose some. It happens to all of us.

However, I met a guy once who didn’t initially appeal to me and we are now married. Once you get past the talking phase and give some guys a chance, they can grow on you. Have a nice day.

Well, did you make any agreement or plans to go out on a date or anything at this point? Because I'm wondering if you actually said anything straight up that would make him think you liked him as more than just friends. I'm just saying because if you kept it at a basically friendly level, you don't have to say as much. But if you did lead him to think you two were going to go out, then I guess you'd have to be more blunt about it.

Update:I agree with the answers provided sometime after mine that mentioned trying to delay your responses to him. I wasn't sure if you've tried that already, but if not do try to delay some. He might do the same, or quickly get the hint. If he doesn't seem to be getting the hint at all though, then I guess you'll just have to tell him something, nicely. But it shouldn't be a big deal if you haven't gotten close to him, so no need to worry about it.

You can’t worry about hurting his feelings because no matter how you do it, his feelings will be hurt. Better just to be straight up and get it over with.

Stop responding.
If you can’t do that, wait 24 hours to respond to any text.
Make your responses as short as possible and then taper off, taking longer to respond and giving shorter and shorter responses.

Tell him you don’t think you have much in common. That’s the issue, right?
He might disagree, but he’ll know what the issue is. And it’s not about him.

Just tell him how you're feeling, that you are not interested because you feel that you want a partner that has more in common with you.