74 70hp Johnson idle problem (SOLVED)

[Bass Runner]

Im having a wierd idle problem, out of gear it idles just fine but put it in gear and it just looses power and dies unless you gas on it real quick, above idle it runs like a champ plenty of power. The motor has about 110lbs of compression + or - 2 or 3 lbs. new plugs, did a link and synch and the carbs have just been cleaned, this thing has me baffled, the only way you can get it going is start it, warm it up then just throw it in gear and go, makes it real rough in the idle and no wake zones, got one ticket already, tried to tell the lake patrol what my problem was and all he said was get it fixed before i come back. any ideas.

 

[ob]

Re: 74 70hp Johnson idle problem (SOLVED)

Does that engine have fixed or adjustable idle jets?

 

[Bass Runner]

Re: 74 70hp Johnson idle problem (SOLVED)

It has fixed jets and when rebuilt i check to make sure there was not a obstruction in the jets they are clean as a whistle, checked for intake leaks and found none this is wierd. It is a 1974 70hp model 70ESL74M if that will help.

 

[papasage]

Re: 74 70hp Johnson idle problem (SOLVED)

i had that probablem with a 50 hp . it had a exzoust leak into the cover . mine was a eletrick shift and the seal around the wires wer gon . sealed it with silacon . it could be the gasket where the foot meets the power head . mine would run good with the hood off . try that and look for exzoust .there is no oxygen in exzoust . papasage

 

[Bass Runner]

Re: 74 70hp Johnson idle problem (SOLVED)

I changed the gasket on it when i rebuilt the water pump, it was doing this before all this, what i can't understand it will idle all day in neutral but put it in gear and if you don't gas on it it will die,

 

[steviecops]

Re: 74 70hp Johnson idle problem (SOLVED)

Does your thermostat work properly?<br /><br />My engine will do that until the engine is up to the correct temperature, then it will will idle in gear no problem.<br /><br />Good luck<br />Steve

 

[Bass Runner]

Re: 74 70hp Johnson idle problem (SOLVED)

The thermostat is new and it dosn't matter if the motor is warmed up, it won't idle in gear even after 30min of wot, i could understand it not idleing if the motor was cold but it won't idle in gear either way, it just will idle in neutral. When i have a problem it's a dandy.

 

[ob]

Re: 74 70hp Johnson idle problem (SOLVED)

If all else checks out ,it sounds like it is synchro related.On my later model 70 hp the carb flaps begin to open slightly, before the timer plate begins to advance.Perhaps you can exeriment a bit with the linkage setup until you can find a sweet spot.

 

[Bass Runner]

Re: 74 70hp Johnson idle problem (SOLVED)

OB if you are talking about link and synch i did that first thing when i reinstalled the carbs, it acts like it is sucking air at idle but i have checked the intake and cases all are sealed and not sucking air anywhere, this one has me baffled, i checked timing and plugs are gapped, like i said other than idle in gear it runs like a new one, tomorrow i am going to borrow a set of carbs and try them they are off a 76 model and were bandnew about two months ago maybe that will help me narrow it down.

 

[Bass Runner]

Re: 74 70hp Johnson idle problem (SOLVED)

Well now the problem has narrowed, i borrowed the carbs and put them on even with the old gaskets the motor ran like new, smooth idle in gear and never ran better, what in the world can be wrong with my carbs, i took them off the manifold and took two of them apart and can find nothing wrong with them, soaked the manifold and checked it with black light and no cracks, any of you carb whizes have any idea what can be wrong.

 

[papasage]

Re: 74 70hp Johnson idle problem (SOLVED)

change 1 carb at a time see what carb it is . i have some extry carbs if need one to rebuild . and they might be allrigh as i just bought a bunch of 70 hp parts . papasage

 

[Bass Runner]

Re: 74 70hp Johnson idle problem (SOLVED)

Now I have taken all 3 carbs down to nothing but pieces and can find anything wrong, all float settings were good and all jets were clear not one speck of crud anywere what in the world could be the problem, guess i'll get new jets and try that, this is getting old when you can't fix a problem like this i have been a wrench for years and this thing has me pulling my hair out what little i have left.

 

[Bass Runner]

Re: 74 70hp Johnson idle problem (SOLVED)

OK i have took all three carbs apart and all the float settings were good and not a speck of crud anywhere all the jets were clean as a whistle, this thing is driving me nuts, i have been a wrench for years and this has me pulling my hair out, guess i will go get new jets and see if that solves it. Man i need help on this one.

 

[Dhadley]

Re: 74 70hp Johnson idle problem (SOLVED)

New jets of the same size wont change anything unless yours have been drilled or altered or are not clean. Different size jets may solve the problem by re-jetting but buying a handfull of jets gets expensive.<br /><br />How about the throttle shafts? Look real close where they go thru the carb body to see if they or the body is worn. Try to move them back and forth. They should remain centered. If they move they could be sucking air thru there.

 

[Dhadley]

Re: 74 70hp Johnson idle problem (SOLVED)

Did it ever idle correctly?<br /><br />What fuel and plugs are you using?

 

[Bass Runner]

Re: 74 70hp Johnson idle problem (SOLVED)

It ran like a new motor with the borrowed carbs but checked the throttle shafts and jets rechecked the float settings, checked the needle and seats and no trash really looked like new, blew out all ports and put it back together and put it on the motor took it down and put it in the water fired it up ran like new at idle, put it in gear and it died just like before and warmed it up good and put it in gear it died, the third time i just stuck it in gear and gassed on it ran it for about 30 min at wot then when back to the ramp and tried to idle in it ran for a few seconds and when the boats speed got down to where it usally was at idle it died, restarted put it in gear again to get to the bank it died had to manually put it on the trailer, i know there has to be something i am overlooking but what?

 

[Bass Runner]

Re: 74 70hp Johnson idle problem (SOLVED)

Yes it ran fine two months ago then started this crap of dying in gear at idle, i fish all year round when i can, so the boat never sets over a month at a time, so far in the last month i have replaced the, coils, waterpump, plugs, thermostat, power pack, changed lower unit oil, and rebuilt the carbs, then i borrowed a set of carbs from another guy and put them on and it solved the problem, it has to be in the carbs or manifold but i can find nothing wrong with any of the carbs, the throttle shafts are tight and jets are in good shape, all the float settings are right, man i think ive got spooks in them i can't find anything wrong with them.

 

[stairliftoheaven]

Re: 74 70hp Johnson idle problem (SOLVED)

one or more cylinders must be running lean to cause the idle problem. Have you tried using colortune plugs with engine in a drum? you should be aboe to narrow down the rogue carb. If running lean, means big trouble coz u also running lean on oil. U need to sort out the carburation problem before using the motor under load otherwise u in for big trouble! I've been there.<br />best of luck

 

[stairliftoheaven]

Re: 74 70hp Johnson idle problem (SOLVED)

on the other hand ur engine could b running to rich which would make little difference at WOT but would choke at idle. I thought u may have a problem with a leaking choke solenoid but ur friends carbs sorted out the problem so thats eliminated that one. if colortune test is ok then problem must be with carb sync.<br />regards

 

[Bass Runner]

Re: 74 70hp Johnson idle problem (SOLVED)

I took the carbs to a omc mechanic friend of mine, told him the problem and ask him if he would look at the carbs, also told him about borrowing the carbs and the results, he let me use a set of carbs off a old evinrude he had there for parts, and said he would look at them in his spare time, came home and put the borrowed carbs on and tryed it, worked like a champ, I called him last night and he said just leave them on there(man i like this kind of tech) and he would just keep my carbs for parts and i told him to go ahead and check the carbs so i would know what was wrong with them he said he would and let me know.