Jack Plate/RPM ??????

[ally260]

Yes it does. Thought maybe you had already checked tha throttle plates. Ya can just have someone mash tha gas petal (motor not runnin' ) then see if ya can move the linkage on tha carbs any farther by hand. Does tha thing ventilate any at all when ya take off from idle? Just sounds like tha motor isn't being all it should be, thus tha low rpms. That combination is close enough to not have these issues I would think. Might be time ta start lookin' at tha motor stuff ie: compression, fuel delivery and electrics. Ya gonna have ta just keep peckin' and askin' questions.
Forgot ta ask if it did this before ya bought it (test drive maybe or not). Has it ALWAYS acted this way? Before AND after ya bought it............T