What is the right jet for my engine?

[DanOnTheBoat]

So I have a few spare main jets for my carburator for 120 Merc. Right now I have #70.9 jets in carb. Tried to look online to see what the factory jet is for the engine carb and can't seem to find it. Figured i'd try and get advice/help here. What is the factory main jet sizes for the Merc 120 carbs? What happens if I leave the 70.9? Is it better to change them to the factory ones(If they aren't)?