First mockup of the exhaust, being a 4 stroke it doesnt need an expansion chamber, all piping is the same ID as the exhaust port, and muffler is a glasspack for 1/5 scale buggy tuned pipe stingers...so rated for 25-30cc motors... i am thinkimg of extending the pipe so the tip of the can is roughly even with or slightly protruding from the back of the boat, to keep any oil drips off the boat...