I believe you are talking about Part Number 328543 – ID Number 58D – Orifice Size 0.058 inches – 1/4-20 thread size, and there are two of them. I see no reason why you can’t drill them out larger, but my experience doing this with a couple of snowblower engines I modified taught me that one numbered drill size can make a very significant difference, and it’s easy to get too rich. I’m curious as to why you want to do this, if you don’t mind my asking . Are you converting it to run on E-85?..or converting it for a racing application?
Dave
The two jets are parts #15 in this view: http://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1998&hp=90&model=J90ELECM&manufacturer=Johnson§ion=Carburetor+%26amp%3B+Intake+Manifold
And this is the part: http://www.marineengine.com/newparts/part_details.php?pnum=OMC0328543
