I have a question about the idle adjustment knob on the tiller of my tiller motor. I'm assuming by the name, it is supposed to be adjusting the idle but my knob does not appear to be affecting it. Is turning the knob supposed to have a very noticeable effect on the idle or is if for very slight changes? I feel dumb asking, but I don't think mine is working properly. Thanks. Motor is an Evinrude E30TELETA.