1992 johnson 120hp idling problem

[h2rick]

resently upgraded the 1988 90hp evinrude with a 1992 120hp johnson,checked compression before buying, was about 140 all around and sounded great with miffins out of the water, I dont exactly know what to call what it does,but when idling and slow traveling it backfires, spitts, or like misses,makes it hard to manuver around the marina,when it spitts it shuts off, other than this engine runs great. I rebuilt carbs,replaced reeds,cheked and double checked lever adjustments,checked circulation system,fuel delivery,primer selanoid leakage. only thing I could think of to check is the idle and high speed timing but I dont have a test prop so I dont know how I could do this on a running boat,also let me note that the engine was removed from boat that it was bought from,and installed on my 17 foot dusky with an adjuster jack plate,could the height adjustment of the engine have something to do with this ? please advise me on other things to look out for.THANKS

 

[Dhadley]

Re: 1992 johnson 120hp idling problem

What's the rpm's in the water, in neutral? What spark plugs are you using?

 

[h2rick]

Re: 1992 johnson 120hp idling problem

the plugs are champion QL-77JC4, I have not checked the RPM in the water, but I CAN DO IT REAL SOON.

 

[h2rick]

Re: 1992 johnson 120hp idling problem

Ql-77jc4, Will Get Rpm Info Real Soon.

 

[sailfish252]

Re: 1992 johnson 120hp idling problem

First take the air box off and make sure the throttle plates are fully closed. If not loosen the screws on the link bar and the screw on the cam follower. Lightly push the plates closed and tighten the link bar screws. Then with the roller just touching the cam tighten the roller screw. Also try to trim the outboard to make it level at idle and see if that helps. You may have raise the engine a little. If you do raise the engine make sure it pumps enough water at high speed so you do not hurt it. GOOD LUCK

 

[Dhadley]

Re: 1992 johnson 120hp idling problem

Remember, this is a looper - not a crossflow.

 

[h2rick]

Re: 1992 johnson 120hp idling problem

what does it mean when you say its a looper and not a crossflow? and by the way thanks for the help.

 

[h2rick]

Re: 1992 johnson 120hp idling problem

I have checked and double checked the throttle plates, they are ok, Iwill see if I can put her in the water this week and try different engine height plate adjustment,the other day the parts guy at our local johnson dealer mentioned that to me,he said it could have to do with the back pressure caused by the water.thanks for the help.

 

[James R]

Re: 1992 johnson 120hp idling problem

You need a manual. The slow running or idle needs to be set up in the water with the motor in forward gear. You can do this with the boat on the trailer with the motor in the water.

 

[mhg]

Re: 1992 johnson 120hp idling problem

This is commonally called a sneeze
my 140 did it
remove the air box and use a towel to block the air intake at each carb
If you find that one particular carb is the problem, then you can find
where the lean condition is coming from
you must be patient and methodical to find the problem
Mine was in one carbs idle air circuit
yours can be anywhere in the intake circuit
when you I.D. the cylinder swap 2 carbs and see if the problem moves to isolate the carb from the intake

 

[h2rick]

Re: 1992 johnson 120hp idling problem

I got the mannual,and it details how to adjust the idle timing, and thanks for the idea of doing it on the trailer,I was also thinking of tying a rope from the bow to the dock and idle it in reverse. thanks for the advice

 

[h2rick]

Re: 1992 johnson 120hp idling problem

when you say block the air intake ,do you mean bloking the idle air orifice,or the carb's whole intake? and why do you think they use #34 orifice on port side and a #37 orifice on starbord side for idle air from factory?

 

[daselbee]

Re: 1992 johnson 120hp idling problem

I had this same issue...called a "lean sneeze" at idle on a 1996 200. The shop worked on it for days...never got it fixed right. So, I am saying that this problem is hard to fix.
But, on 2/6 9:26, dhadley says "Remember, this is a looper - not a crossflow."
Dhadley, what exactly do you mean by that?

Is a lean sneeze diagnosed differently on a looper vs. a crossflow?

Please elaborate on this statement. (no one liners please)

Thanks.

 

[Dhadley]

Re: 1992 johnson 120hp idling problem

Someone was giving advise on how to set the throttle plates on a crossflow. The 120 is a looper and the linkage is different.

 

[Dhadley]

Re: 1992 johnson 120hp idling problem

And yes, backpressure has a lot to do with it. That's why the idle has to be set in the water. In neutral, in the water it'll be 800 or so. In gear, in the water it should be 650-700. Out of the water, and once it comes out of Quick Start it'll probably be around 1100.

If you try to set it ay 800 out of the water it'll likely do what you describe once it's in the water. If it is spitting back thru the carbs with the idle set right you'll be looking for an air leak. If it's popping back thru the exhaust it could be an air leak or something else.

When trying to isolate an air leak you can use toothpicks to plug an idle air bleed. If the problem is an air leak don't overlook the plates on the side of the carb. That's a very common place for an air leak.

 

[daselbee]

Re: 1992 johnson 120hp idling problem

Someone was giving advise on how to set the throttle plates on a crossflow. The 120 is a looper and the linkage is different.

Thanks dhadley. So I will ignore the above instructions regarding throttle plate setting and strictly use my Evinrude shop manual for link and sync issues.

I was thinking by your cryptic quote about looper vs. crossflow that there were different reasons for a lean sneeze for loopers vs. crossflow.

Couldn't his lean sneeze be simply the idle mixture screw adjustment?
And I understand the toothpick method, but are there any other tricks to finding air leaks...???

Thanks in advance.

 

[Dhadley]

Re: 1992 johnson 120hp idling problem

The 92 V4 loopers didn't have adjustable jets, just the screw in fixed air bleeds. If the air leak - and we're assuming it's an air leak because he's never said if he's trying to set the idle in the water or not - can be isolated to a certain carb or cylinder you can spray fogging oil around the suspect area.

The idle on a looper is very simple to set but it has to be done correctly. If the plates are not seated - for any reason - it will always be wrong. I believe he said he got the manual and if he starts from scratch he'll find the problem pretty easily. A lot of people start turning the screw in the throttle arm and that just messes up the linkage.

 

[daselbee]

Re: 1992 johnson 120hp idling problem

Thanks dhadley,

Sorry about the idle mixture question...I have a '98 225, and they have the mixture screws.
Thanks again for the tip about fogging oil.

 

[h2rick]

Re: 1992 johnson 120hp idling problem

I am truly amazed at how many people have had this type of problem , God willing this weekend I am going to put her in the water, since I rebuilt the carbs with new rebuilt kits, and replaced the reeds with new gaskets , and checked complete circullation system, I really doubt it to be an air leak,but lets not rule anything out,I've been a mechanic for over 20 years and have seen some real funny things. onece in the water, I will follow the idle adjustments down to the wire, and if it dosent do any good will try the height adjustment, even the tooth pick thing, I thank every one for their input and help, soon as I do these things I will post the results. By the way could anyone tell me why it uses a size 34 idle air orifice on port side and a 37 on starbord side ? thanks again

 

[Dhadley]

Re: 1992 johnson 120hp idling problem

BTW - when you're checking out the jetting, don't run the motor under a load with the airbox cover off. Letting it sit there and idle is OK but if you put it in gear and try to run it under a load you'll be changing a piston or two. That motor will lean out real quick........