2011 sundeck 240

I just purchased a 2011 sundeck 240 with 5.7 mercruiser. Only 60 hours on the engine. I previously owned a 1999 sundeck 210. 700 hours on the mercruiser 5.0 without a problem. First time boating in the 240, I got an engine alarm that there was an exhaust issue, and something about a bad oxygen...