I just purchased a 2015 Sv233 this year with a 450 pcm. I have been in boating for many years and really liked all the new technology, fit and finish that Centurion had added in the last few years. Every year we send a week on Lake Powell using the boat 8 hours a day. At the end of the week every-bodies head was ringing and the $6500 downfire sound system we paid for was wasted. I tried a FAE, but didn't like the spray of the wake. I found a company called GGB out of Canada, they make a insert for a 4" exhaust which slipped right into the stainless steel tube ( which is a empty tube) located in the exhaust hose before the exit flapper inside the boat. I purchased a pair of 8.5 inch inserts, but found i only need one installed. The boat retains the stock look, but the noise is greatly reduced. I lost about 100 rpm on the top end, which was more than acceptable to me for the noise reduction. They also make a 5.5 inch insert which might not effect the rpm, but might be a bit louder.
Just thought all those out there struggling with how loud these boats are might want another option!
I also have an extra 8.5 insert if someone would like to pick it up from me, $90.
Love the boat and now my ears aren't ringing!