1988 ProV150 is very loud

[slick3783]

I have a 1988 Yamaha ProV150 on my 1987 Venture Regatta bass boat. Bought this boat a few years ago and have noticed that it is a lot louder than other 2 stroke motors. The boat will run 68-70mph with no passengers, so no problems with it running, it's just loud. After I bought the boat I removed the carbs and cleaned, and after cross-referencing the numbers, noticed that the carbs were off a Yamaha 225 Excel. I looked at the heads, and they were also off of a 225. I'm assuming that a previous owner had done mods to this motor. Is there a possibility they done some type of mod to the exhaust system? If so, is there a way that I can replace something to make it quieter while running?

[boats.net]

Without knowing what has been changed be hard to say, probably have to take apart and see if muffler has been changed or altered.