JOHNSON 115 WONT STAY AT CONSTANT IDLE SPEED.

[BOATRIGHT]

I have a 90 year model johnson 115 that I bought rebuilt .The motor runs great except it will not idle fo any lenghth of time and is hard to start sometimes.I recenctly put carb kits in both carbs with no improvement.Would increasing the idle intermediate jet size help? i have a 90 year model rude 90 horse so i changed the electronics from the rude to the johnson to see if that would help it did not.

 

[Chum Slick]

Re: JOHNSON 115 WONT STAY AT CONSTANT IDLE SPEED.

I don't how similar the motors are but I recently had a 1980 115 hp Johnson rebuilt. After installing the powerhead it ran fairly good at higher rpms but would not idle and was hard to start. I checked everything on that motor and was about to go crazy trying to find problem utill I gave up and took it to local Marine mech. He found the flywheel key was broken which was causing the timing to be inadvertently jumping. Changed flywheel key and now it runs great. Don't know if that is your problem but if all else fails may be good to have it checked.....Good luck...<br /><br />Keep the bait in the Slick.........

 

[Yepblaze]

Re: JOHNSON 115 WONT STAY AT CONSTANT IDLE SPEED.

Sometimes it takes more than "putting in carb kits" to correct fuel delivery problems. ".nullIF" it is in fact still a idle mixture problem it may require more attention to the passageways within the carb bodies to correct the problem

 

[BOATRIGHT]

Re: JOHNSON 115 WONT STAY AT CONSTANT IDLE SPEED.

Thanks for the response.Chum slic I know it is not the flywheel key I had it off when I changed the electronics on the motor.YEP BLASE the carbs looked very good on the inside but I used a can of cleaner on each one.The kits came with what looked like caps or plugs 2 for each carb.I saw where I assume they go, buy did not know how or if I needed to remove the old plugs.if i need to how do i do it thanks for the help .

 

[Yepblaze]

Re: JOHNSON 115 WONT STAY AT CONSTANT IDLE SPEED.

Usually those plug items that might resemble small freeze plugs might be to plug off the drilling access holes needed during manufacture. Not necessarily something you should need to, or want to tackle removing as getting a good seal during reinstalation can be tricky at best. But you might want to go back and check to make sure any slots or holes inside the throat(s) near the butterflies where the mixtures make the idle feed, and transitions to off idle might have a bit of crud. If you have while doing the carbs, sprayed the cleaner through all passageways noting the flow characteristics from one carb to the other and feel confident that there are no obstructions then it must be assumed you took the carbs out of the equasion. Does it spit much gas back through the carbs at idle? (reeds)<br /><br /><br />I notice you said that it would not idle for long. That might lead one to think it might be still leaking needle/seat problem. But how after they have been replaced? Unless one of the bodies has a leak above or around the seat area. (I have actually seen that on a small engine carb once)

 

[BOATRIGHT]

Re: JOHNSON 115 WONT STAY AT CONSTANT IDLE SPEED.

Yepblaze the motor does spit or I would call it a burp when you try to start it cold and sometimes warm.It takes many attempts to get it to start running without it burping and then shutting off.

 

[Yepblaze]

Re: JOHNSON 115 WONT STAY AT CONSTANT IDLE SPEED.

Lets change that word "burp" to "sneeze" if applicable and it would describe a lean condition. <br /><br />If that is in fact the case, start looking for an air leak. The old spray wd40 around the crankcase mating surfaces, carb, and reed plate while running might show an improved idle. While you are at it try a little in the intake(s) while idleing and look for improvement.<br /><br />Could it be that the idle circuits are still a little bit plugged causing you to maintain a setting at the butterfly above the idle circuit to maintain an idle? How responsive is the idle mixture srews when trying to dial it in?

 

[BOATRIGHT]

Re: JOHNSON 115 WONT STAY AT CONSTANT IDLE SPEED.

yepblaze the carbs do not have a needle adjustment,instead it has 2 air fuel orfices,2idle intermediate jets and 2 high speed jets.I will have to try spraying wd 40 and see what shows up.if I increased the idle,intermediate jets would the sneezing GET worse?

 

[Yepblaze]

Re: JOHNSON 115 WONT STAY AT CONSTANT IDLE SPEED.

I wouldn't be sure.<br /><br />But sneezing is usually associated with a lean condition. And I have found if the idle circuit isn't working properly, and I open the butterflies enough to try tomaintain an idle it only becomes that much more frustrating. <br /><br />I'm sure others here can chime in with some other things to be considered.

 

[Yepblaze]

Re: JOHNSON 115 WONT STAY AT CONSTANT IDLE SPEED.

My Suzuki would sneeze, crap out and not restart till I reduced the plug gap. Since then it has not been an issue at all. Kida a cheepie workaround from buying parts.

 

[BOATRIGHT]

Re: JOHNSON 115 WONT STAY AT CONSTANT IDLE SPEED.

Yepblaze what was your gap, and what did you change it to thanks.

 

[Yepblaze]

Re: JOHNSON 115 WONT STAY AT CONSTANT IDLE SPEED.

Don't recall what it called for but a tight .020 and I haven't given it much of another thought since. Being as it fires both plugs at once, through one, and out the other to cmplete the circuit, I figured it might be the coil that's bad. I called and priced a coil once. But heck, if it is happy the way it is so be it.