Anybody know where you can get rubber exhaust "S" pipes? I saw the cast and stainless ones, but I know I saw rubber ones before just can't seem to find them.

I've never seen them. A rubber elbow will burn through in no time making a very dangerous situation. Stick with stainless.

I know what you mean. But I thought I saw some high temp silicone ones being used. My problem is I have 6" to the transom and I need to go below the rub rail. I can go down plenty but going out (towards transom) is only 6". Does anyone know how long the stainless or cast S pipes are from either open end to the outside of the 90(or bend)?

There is a company named JAGCO - 270-554-2626 - their primary line is flexable exhaust for automotive and commercial engines. Call them, the owner is name Joe, I am their CPA, see if he can help.