SMI tail pipe exhaust leak issue
 

I have just recently replaced two small blocks and purchased some used smi 4 inch exhaust. I now have about 15 hours on the new motors but I am having an exhaust leak every time I run the boat at higher rpms (4000). Motors are rated for 5200...During break end period I ran boat ( First ten hours) steady at 3500 with no problems. But I would check for loose bolts after ever run and I noticed that I had to tighten the tail pipe clamps every time. Now I am starting to push the rpms and I get an exhaust leak at the the tail pipe clamp seems every time I try to push the rpms...Is the bolt stretching or just loosening up I don't know? Should I replaced the used clamps? Exhaust leaks sound really bad....This is happening on all four tail pipe clamps. Do the clamps just wear out? Thx 4 any advice...r

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