attaching muffler with U bolt. do i need cement?

You are not getting a good seal. Get a tube of muffler cement, pull the joint apart, slather it on and reassemble. The water leaking out of the joint is troublesome. Is it just condensation?

If the pipe is that deformed you could try to reshapt it. This takes an expander to do the job right and you don't have one, right? Any other method can result in making the thing so bad you can't get the pipes together. So yes, you could smear gobs of Victor Muffler Cement on it when putting it together. Mostly though, you are not putting enough muscle on the clamp to squeeze the pipes together. Tightening it hard enough should do the job.

interesting

Its condensation but from inside the muffler leaking out. Don't think i can get it off now. Muffler pipe has a groove now that mates with existing groove in pipe that i am attaching muffler too. All is lost.

Ok, i will tighten harder. I think i agree with you from past experience with plumbing applications. It's all about arm muscle power which i lack.

The new connection will rust up quickly and seal small leaks. A tiny drip of condensation is not a huge problem. New mufflers have a weep hole to drain water.

I tightened some more and it does not leak anymore. ya!

Thanks. No more leak.