The people that write the owners manuals and assemble the boats haven't got a clue to where they are headed to so they give you a general starting point. Weather and altitude among other factors decide where the settings must be at on your boat. Try opening the high-speed needle a little more until it fires up and runs right. You'll want it on the rich side until the motor breaks in, you should see some oil smoke coming out of the pipe or a little unburned fuel exiting.
The idle set screw on most boats generally isn't needed except that a lot of times it holds the barrel from sliding out. You want it set so that the carb will fully close, the throttle trim can do the rest.