Ex heavy smoker, not a bad stutterer here. In my case marijuana did not help (or any other kind of drugs) with my stuttering. It even made it worse sometimes. Yes you will get relaxed, very relaxed to be honest. But for me it did not help. If you never tried marijuana than keep it that way. Dont smoke it cause there is little chance that it will help. But there is a high chance that you will get addicted to it or maybe try other drugs. Btw: I don't (95% of the time) keep repeating letters or words, I just have strong blocks. It does not help with blocks, maybe it will help with for example e.e.e.e.e.e.e..e.e.e.e.e.e example but not with total blocks.