85 johnson 20 wont idle

[larryg]

i am having a problem with the engine not running at idle.i have taken the carb apart twice, put new carb kit on it.new fuel lines cleaned and inspected fuel pump,which pumps ok.when i did the synchronization it didnt help either.when the cam follower is between the two marks it wants to completly die.as i advance the throttle it cuts out for a second and then takes off and runs perfect. 2nd question was i needed an explanation on:step 3 on throttle control rod adjs.throttle plate should be at full open position at this point,but not binding throttle shaft.the binding part wasnt sure of.thanks for the help

 

[fireman57]

Re: 85 johnson 20 wont idle

I assume that this is a tiller handle. There should be a big screw that goes to a stop on the throttle arm on the left side of the engine as you look at it from the front. You may just need to screw it in more or less for your idle.

 

[larryg]

Re: 85 johnson 20 wont idle

i have done this with the idle adjustment on side.when i get it right and put it in gear it runs very high,such as being wot.and i cannot turn tiller enough to reduce it,it is maxed out.

 

[ONERCBOATER]

Re: 85 johnson 20 wont idle

thinking the "as i advance the throttle it cuts out for a second and then takes off and runs perfect" sounds like your low speed mixture is lean, causing it to bog initially then as the highspeed jet cuts in return to an acceptable fuel air mix.
suggest you get her running in a 50gal drum or off back of boat in the lake (or body of water of your choosing) and adjust the idle mixture screw out until it runs smoother at idle... suggest you do this at the lowest speed you can keep it running at until you find that you can lower the speed again.
keep in mind that the idle speed mixture screw is turned via the knob on the front of the engine, and that after you move it so far the knob will have to be pulled out a bit so as to allow it to rotate past the stop. when you get it set properly for a now warm engine put that as the middle position (by pulling the knob off and replacing it oriented as you need to) then set it richer when you go to start it cold. and you should have it licked.
if adjusting this screw does nothing at all then you have a different problem or that circuit is still dirty.
give it a try if you will and report back.
the screw that fireman57 is talking about is also a possibility as it is most often used for idle speed control such as when trolling.

I used these diagrams to double check on tha carb....http://www.boats.net/parts/search/BRP/JOHNSON/1985/J20ECOS 1985/parts.html
but would suggest if you need parts ordering them here at iboats instead to support this great site and forums.

Sean

 

[ONERCBOATER]

Re: 85 johnson 20 wont idle

oh other thought, set your idle speed adjust screw while in gear on warm engine. that is what it is supposed to be for... so that you can troll, or maintain a fixed repeatable speed in gear. from my exp, engine should not die with it at it's lowest setting if timing and fuel mix are correct.

 

[larryg]

Re: 85 johnson 20 wont idle

i will try this as soon as i get the chance.i thank both of u for the support.i will let u know

 

[fireman57]

Re: 85 johnson 20 wont idle

Oner is right, I forgot to tell you to set things while you are in the water. The back pressure makes all the difference in the world.