Somewhere around ’57 or ’58 OMC switched from the aluminum primer button to the larger plastic button. If you are using the later diaphragm in the earlier tank, you will have to punch a small hole in it for the aluminum button to go thru. With this design, you should also use a fuel proof sealer of some kind on the cup washers and threads of the button to prevent fuel from leaking thru. The sign of a leak is fuel mix coming out from around the button when it is being pushed. Some 10-24 screws with the heads cut off can be used to help keep everything in alignment when reassembling.
