Its more common on the later engines, and Mercury will be issuing a bulletin on this issue soon after they issue one on the 250 pro XS. They are aware of the issue, and are working on it, but at this time havent covered the issue with the dealers. It is a miss at around 1100 rpms and is bothersome, but not terminal. Performance is still good on mine, just sounds bad at high idle ! But its still the best engine on the water ! D.