I just removed my Gibson "donkey Dong" mufflers about 2 weeks ago from my boat. They made the boat quiet at idle (off-plane) but it just wasn't worth having water soak the back half of the engine hatch. My wife was sick of getting soaked every time she went back there to attach lines. The cops around where we boat don't enforce it. We passed by DNR two different times yesterday within 25 feet in no wake zones and they didn't mess with us. I had it tested before installing the donkey dongs and it registered 110+ on the the meter.
Take it to court and ask the cops what the ambient noise registered before you started your boat. Gets 'em every time because they never check it!!!!