Not running a waterbox will not make more power, the pipe needs a certain amount of back pressure to work correctly. What usually happens is some non knowing fool runs his boat without a waterbox and now that it makes more noise, so it must make more power, WRONG!!!!! Now everyone hates jetskis because their loud and so we get banned from another riding spot all because some guy who doesn't know how a jetski two stroke works. If you want the best responce and best power get a gp760 waterbox, but don't kill your power by not running a waterbox.