1985 Johnson 9.9 will not idle?

OK I just received a 1985 Johnson 9.9 J10ELCOM motor.
Ran the motor last sunday no issues. fast forward to this sunday motor started fine used for a while changing spots
i dropped the handle and the motor stalled out and would not start. Thought maybe it flooded so waited a while.
still nothing. Figured out a way to start was pull the choke in and out while cranking once it starts put it in gear and punch it seems to only stay running from half to full throttle any lower it stalls.
The first time i ran the oil/gas mix was 100:1 as indicated on the motor. the second time oil/gas mix was 50:1 as indicated by the marine repair shop, they said the motor was made with that sticker but take it off and run 50:1.
It has new NGK plugs, new fuel line.

Any help would be appreciated.
I did not turn slow speed adjustment nob not sure exactly what that does.
Could it be a clogged jet?

Re: 1985 Johnson 9.9 will not idle?

The shop was correct in advising you to use the 50:1 ratio.

I would swap out the plugs and run Champion L77JC4 as per the manual.

The slow speed adjust directly affects idle performance. Turn it in (clockwise) until it seats gently, do not overtighten. You will have to pull the knob on and off since there is a stop that prevents it from turning all the way. Once it's in all the way, turn it back out (counter clockwise) 1 and 1/2 turns. That's a ballpark setting that should allow it to idle somewhat. You'll have to adjust it to get the best idle.

If it still does not want to idle good, you'll most likely have to pull the carb and clean it out thoroughly. That includes removing the welch plug on the carb to clean the low speed passages. If the low speed passages are clogged then the motor will not idle well, if at all.

Check out this website, tons of great info the the 9.9/15 HP series:

http://www.sschapterpsa.com/ramblings/Johnson 9.9_15.htm

Re: 1985 Johnson 9.9 will not idle?

Thank you. I will swap the plugs and try to mess with the slow speed adjustment. Hopefully that will work. If not i will order a carb kit gaskets and check that out.