Well, first off, you have not posted the model number. There are numerous versions of the 115 in 1998.
But that aside, I will now guess that your model number is a common one, and i will consult the parts pages at
shop2.evinrude.com to look up this info.
For a E115SLECM, the intermediate air bleed orifice is a number 20 orifice, and is replaceable by unscrewing from the front of the carb face.
The main jet is located in the float bowl, at the bottom, behind the main bowl drain screw. It is a number 73 orifice.
The idle adjusting screws, AGAIN GUESSING, would be set to 5 - 6 turns out as a starting place.
As suggested above, download or buy a hard copy of the service manual. You will be very glad you did, as it has very speific answers to questions exactly like yours.
If the above info is NOT for your model number, look the info up yourself at shop2.evinrude.com.