johnson 120 wont idle

[mwagne30]

fresh powerhead, top end good, mid range good, hot or cold at idle it will sneeze/cough and die, I can hold my own with tools and all I would like to do is help out one old man who seems to have been run through the cleaners, to the toon of about $3000- $2500 for the power head $450 for a new battery and starter,which still seems to turn this over way to slow, bad ground? My neighbor is always letting my son (13) tag along with him, andnothing would make two fishing buddies more happy! so let's start 1991 johnson 120 hp fresh powerhead- this thing ran well before it was run out of oil did I mention that the old guy is hard of hearing? like I said top end good, run strong sound strong. but at idle hand it a tissue sneeze and cough and die. dealer wont even talk to the old man I even had a crack at it and was told it's old. and I asked even with a fresh powerhead? with less than 2 hr on it give me a break!!! at this point he won't even take it out for fear of it not being able to make it out from the ramp at an idle Please help!!!!

 

[tashasdaddy]

Re: johnson 120 wont idle

sure sounds like carbs to me. low speed jets.. what's idle rpms?

 

[mwagne30]

Re: johnson 120 wont idle

It will hold about 600 /800 rpm to low?

 

[mwagne30]

Re: johnson 120 wont idle

It will run around 600/800 rpm To low?

 

[mwagne30]

Re: johnson 120 wont idle

It will hold about 600/800 rpm to low?

 

[robert.barnes]

Re: johnson 120 wont idle

i also have a 120 looper and i have all kinds of trouble geting it to idle and run right but this is were i have got mine lined out thanks to every one here so i will see if i can help u out. if they r the original carbs the ones that came with the motor i would take the throats off (the black plastic part) and clean the crap out of them maybe even kit them if the motor set very long just because it has a new power head does not mean the carbs were rebuilt when u take them off look on the back side and there will be a o ring on the back with two little o rings sticking out make sure they were not pinched if they were that might be your prob it sounds like the motor is sucking air causing it to run lean u may need to just clean and kit them i would try that first

 

[mwagne30]

Re: johnson 120 wont idle

That I can do, will start soon,Carb kit sound's easy? would it help to have them steam cleaned at the local hot rod shop? or will these melt? and what is a standard setting for the jet screws? like 1.5 back from seat ? thanks for the help I also see that we have a few different supplier's do we stick with OEM or are the aftermarket good to go? we looked on line at $ and all seem to have on hand,and from what I understand I need four right? one for each carb? thanks from the non boater

 

[bigbob_FTW]

Re: johnson 120 wont idle

the rebuild is not hard, however, i would not steam clean them. Soak them overnight in b-12 chemtool and blow them out real good.

 

[mwagne30]

Re: johnson 120 wont idle

How about carb kit's OEM/aftermarket can anyone give some advise we can get both overnight if we order by high noon and cost is about the same and I was told that the napa dealer can order this ? is that true?

 

[robert.barnes]

Re: johnson 120 wont idle

i have oem in mine but the after market should work fine does your carbs have the idle adjusment screw or r they fixed jet mine is fixed jet so i do not know what the adjusment would be sorry

 

[mwagne30]

Re: johnson 120 wont idle

4 OEM kit's in the mail don't know about screw yet? till I remove the carbs for cleaning and disassembly, so with any luck we will be back in action !

 

[mwagne30]

Re: johnson 120 wont idle

O.K. Team we rebuilt the carb's on sunday and all look's like we have a winner, I think? right now the old girl will idle at 1000 RPM on the hose with muff's, is this good? or should I try to back it down to the 600/800 that it held before the rebuild? or is it the cold water from the hose? Also found the starter issue, cable on positiveside had nut that seemed to be coated with something, gold paint, varnish? at first glance we thought it was brass, so I ran a clean nut down to the fiber washer added a washer installed the + side and put clean washer and nut on top, now we have some action from that starter,spins with some backbone! now this is a fresh powerhead so how many tanks of (Mix) gas should we run? the Butcher shop- marina told us One would do and change the plugs, wich were supplied, I should add the plug's that were supplied were missing the (Q) in the suffix is this o.k. thank you

 

[hoeser]

Re: johnson 120 wont idle

Your engine will idle much better and faster on the muffs due to a lack of exhaust backpressure. It will probably drop 200rpm just from dipping it in the water.

There are many different break in procedures, I follow the 10 hour procedure... which calls for 50:1 mix + VRO for the first 10 hours, if you don't have VRO you would mix 25:1.

"Q" plugs are supposedly specifically designed for marine CDI ignitions but I use L77JC4's... I'm pretty sure most people do. I can't get the Q plugs around here easily.

 

[mwagne30]

Re: johnson 120 wont idle

Thanks to all that helped!!! we will try the old girl tonight! So if anyone see's two kid's one 13 the other 69, and one more guy chuming that will be us! So wave to the two with the smile's and no I'm not rude just not a water person!! Thank you all from a nonboater

 

[hoeser]

Re: johnson 120 wont idle

What lake are you on ?

 

[mwagne30]

Re: johnson 120 wont idle

Tonight we will be on Lake St.Clair,By Mt.Clemens Mi at about 6:30 and No I will not be the main attraction!! now Tuesday the two of these jokers would love to show off my handy work,and let them show all of ya! But this Guy is no boater!! the two of them are on a boat called Low budget and my son is capt.Kid/ and the old man is wisker's( He look's like santa ) The boat is a old Lund with a good sounding Johnson 120, so look for those two and ask them who superman is? that would be me the man who saved the day

 

[hoeser]

Re: johnson 120 wont idle

I'm on St.Clair as well but I don't cross the imaginary line for fear of getting shot by scary Americans!

 

[mwagne30]

Re: johnson 120 wont idle

Don't listed to the new's, the city of Detroit has droped to number 8, As these thugs get old the eye sight get's weak and well what more can I say, more missed shot's! We try to tell them to slow down take your time aim pull slow, but you know once a thug alway's a thug. Wich is why I don't go to the city! but I will give them all bullet's! sooner or later we will run out of bad guy's Now let's talk about the real crime, that would be me and what I was doing out on the water, The two I was with saw everything I ate for the last two day's I was so worked up,I hit bathroom on the way out to the water, that's right the boat was still on the trailer, not even wet! She seemed to run well but right at 1500 RPM we have a slight shake 1400/1600 both good not sure yet what that is but I was asked to give it a few day's and let them run a few tank's of fresh gas through the system with some sea foam?, after that we will install new plug's, but we were able to idle out to the marker and around for about a hour and a half and cut it loose, We are running 50/1 plus the VRO is still hooked up I have read alot about this system and it seems to me as a 50/50 like it or not, I think I is much cleaner for these two to fill the tank every day on the way out instead of mixing - (built in tank, how much do we need that might be good, or even listen the fish are in we got to go!!)I must add, For a old boat this girl will run almost 55 mph at 5400 rpm and that's on the gps so I know it's in the park, and hold 35/38 without even working, so it seem's that the powerhead is strong, just need to work out a few more (issues) and that's my job from now on! and I will leave the water to you NUT'S!! thank you very much!

 

[mwagne30]

Re: johnson 120 wont idle

Still have a shutter at or very near 1400-1600 RPM, what do you think? almost like a slight miss any idea's of what to do we will try most anything thank you and how hot should the water discharge line be on this rig? It is to the point that it is hard to hold my hand in the stream, new water pump last year, not a strong flow? but no buzzers,are we still good to go ?

 

[mwagne30]

Re: johnson 120 wont idle

Thank's to all for the help the boat ran well all weekend with no issues, ran in four new plugs and she fine. still seem's to run a little hot for me and water on the out let is to the point of unable to hold my hand in it, but she is running great! this web site is the best thanks to all!!!

from the non boater