Reel.... There is a scribe mark on the cam that slides against the vertical arm linkage that opens the throttle butterfly. The throttle should just start to open when that scribe mark in dead center with the vertical arm.
Joe, I checked the cam on this motor and there is no scribed mark. I rebuilt another 3 hp several months ago and it had the scribe mark. Do you have any idea of the measurement from the small end of the cam to the scrib mark? Thanks THE REELFISHERMAN