I have a new mercury 1999 200 hp 2 stroke that runs rough at mid RPMs. recently bought the boat and before I put it in the water had the lower unit replaces with a Stern Drive Engineering aftermarket lower. have run it probably 10 hrs. kind of followed the breakin process but did troll with it for probably 4 hrs. anyway it runs good at idle and just recently to it to WOT, on 21' seaswirl got to 42 MPH sound good there but at about half throttle it sounds rough and don't know if its lower unit or engine? any suggestions
