Is that the 2 cylinder 4HP? Take the ruined jet and find a replacement that is identical. You can use the jet from a Johnson or Evinrude 4 HP. If you can find the brand of the Carb You might be able to find on online.
this people might be able to help.
http://www.smalloutboards.com/
Keep trying, no one makes a better 4HP motor. That is the smooothest running small outboard motor ever built.