I have the 20 horse beta and the manual shows a dipstick and fill plug. There is only a fill plug with dipstick attached. It is a round rod with a notch in it about a half inch up from the bottom with no writing on it. The manual says the box it " topped off" from the factory. How full is it supposed to be? To the top or to the notch? Looks like it is half wat to the notch, or barley on the stick. The gearbox itself is about halfway full if that from what I see. Talking about the trans forfurther info. How full should it be?