Well, I will jump in here I guess.
To tell you the truth, I would try the easy fix first. See if it works. If not, go thru the whole carb.
Easy fix....go to shop2.evinrude.com, select Johnson, and drill into the parts pages til you get the carburetor drawing up.
Notice reference number 9. It is a jet located in the stbd side of that plastic top plate.
Take a can of spray carb cleaner with a straw, and while running, even above idle if needed, stick that straw directly into that jet, and spray liberally. Spray about half the can, not at once, but kinda intermittently, as the engine will falter and try to die. Let it catch back up, and spray some more.
That will shoot carb cleaner directly into the idle circuit passages, and MAY help the situation.
Next, you have an idle adjustment needle reference number 18. Try opening that up 1/2 turn at a time or so, remembering the turns so you can go back if you need to.
If above fails, report back for more detailed carb cleaning instructions...what to look for, tips, tricks, etc.