Re: 9.9 kicker won't idle
The stablizer, which is recommended by all mfg's now for all size outboards whether 2 stroke, DFI, EFI or 4 stroke is necessary since most gas contains upto 10% ethanol.
E-10 gas actually burns cleaner and ultimately keeps your fuel system cleaner than gas without ethanol but it has one side-effect - it attracts moisture which can separate out and leave water in your gas, filter, carb etc - no big deal in your car because you burn through the gas quick enough that it doesn't get "old" (takes about 2 weeks), but your outboard could run on the same tank all season depending on usage - plus, some gas always remains in the system somewhere.
So yes, stablizer all the time.
Your kicker may be past the point where something from a bottle will help, but give it a try first anyhow. At worst you are going to have to pull the carb and clean it - which would be the recommended remedy anyhow...