It is quite normal for the props not to have the proper hole size. You can use a prop reamer or the proper size drill bit to get it to the correct size. As for your spinner, some of them come with bushings to make it the correct size, or you may have to drill it as well. You will find the reason for this is that your 12 X 6 prop is designed to be used on a number of different engines made by a number of different makers. It appears that no 2 engine makers have the same size prop shaft so the prop and spinner makers start with all the holes being small. Good Luck, Dave