Johnson 70 1986 stalling above idle

[skiers5]

G'day to all boaties out there. I have a 1986 Johnson 70 that starts and idles fine in the water. Idles at about 1150 rpm. Once i have it warmed up with the fast idle, it will sit and idle but one i try to engage a gear and raise the idle it stalls and sounds like it runs out of fuel. Flick the key and it restarts instantly. I moved the carby butterflys by hand, once off idle it has a flat spot then stalls. I've checked for vacum leaks in the fuel line in case it was sucking air some where any suggestions. Any one
Return emails can also be sent to skiers5@bigpond.net.au or dean.cameron1@defence.gov.au
Thanks Best regards
Dean cameron

 

[SparkieBoat]

Re: Johnson 70 1986 stalling above idle

new Champion plugs first...then do spark test on each wire with spark gap tester. (available at auto parts store) should get blue streak at 7/16 gap. then test compression.

 

[kenmyfam]

Re: Johnson 70 1986 stalling above idle

Basic health check to begin with.
Compression
Spark
Fuel delivery
Spark plug condition

See top secret files for the how to's
http://forums.iboats.com/showthread.php?t=299680

Post results.
Welcome to iboats

 

[skiers5]

Re: Johnson 70 1986 stalling above idle

Sparkie, Ken, thank you for the replies. Its running NGK plugs at the moment so I'll replace them with champion copper core marine plugs and gap them at .035" do a compression test, replace the fuel filter and lines, checking the timing arm moves prior to the throttle. Failing that looks like a carb clean,link and sink. Just wondering if it would be more cost effective to take it straight to O/B tech and get them to sort it out. What does a de-carb do for the motor does it clean everything past the carbs or the carbs and reed valves as well?
I have my own stainless test tank to load the exhaust back pressure and prop so I am lucky not to have to travel to test the motor, whats the correct idle speed in neutral and in gear? I have a inductive pick up timing light that I can check to see if the lead is and coil is firing will buy a tester to test gap jump as well.
thanks again, Dean

 

[15flats]

Re: Johnson 70 1986 stalling above idle

Skiers, I did everything you are about to do, I noticed that the Evinrude\Johnson\OMC 70H.P. is plagued with this low idle problem. There were at least 2 other boats out on the water Saturday and did the same thing. When I spoke to them about it, they said the same thing about what was mentioned here (compression,spark,fuel delivery,etc...) but still does it. I even seafoamed mine and rebuilt the carbs. If I throttle 1/2 or more, the engine comes to life, but to idle in gear up to where you are going, forget it.

Please keep us posted as I want to follow your thread to see if you figure out what is plaguing the engine low idle problem. One other member here posted earlier on one of my threads that the needle valve should be changed to (I think) 0.35" to start with and tinker from there. At over $6 a jet valve, I will wait.

good luck!

 

[SparkieBoat]

Re: Johnson 70 1986 stalling above idle

I will be willing to bet the owners of those other poor running motors have not maintained them properly. 2-stroke motors require maintenance and need to be checked often. I believe that motor requires QL77JC4 champion plugs at 030 gap.

 

[15flats]

Re: Johnson 70 1986 stalling above idle

QL77JC4 is what I run, Champions. Had NGK's when I first got it. I believe you are correct on that maintenance also, I changed the outboard oil, when I removed the drain plug, it was like mud (sludge), my motor was poorly maintained, but after all the work that was done it should be running a lot better than it is.

 

[skiers5]

Re: Johnson 70 1986 stalling above idle

Sparkie I think I inherited one those poorly maintained 70s. I bought the the Whiteline open run about with all safety gear, radios, finder gps, and ski gear for kids and adults but the motor had not been started for 2 years. For 2 k Aus I thought it worth the risk. I dont think the problem is going to be major. The more I think about it may be the timing needs to be advanced a little more to to cope with the opening of the carbs and extra fuel. Think I'll try that first.
Dean

 

[skiers5]

Re: Johnson 70 1986 stalling above idle

QL77JC4 is what I run, Champions. Had NGK's when I first got it. I believe you are correct on that maintenance also, I changed the outboard oil, when I removed the drain plug, it was like mud (sludge), my motor was poorly maintained, but after all the work that was done it should be running a lot better than it is.

Did the change of plugs make a difference?
Skiers

 

[15flats]

Re: Johnson 70 1986 stalling above idle

Skiers, changing the plugs,rebuilding the carbs, replacing the fuel lines made the high end much better and starting with idling in neutral. It is shifting into gear and low idle that is the problem, after a few minutes (sometimes that long) it stalls, like it ran out of fuel. But I have noticed that if I go wide open throttle for a minute or two then I can low speed idle without any problems, unless I shift to neutral then go back into gear or shut off the engine.

Do everything mentioned on this thread, the people here are great and know what they are talking about, my boat would not start up before, and now at least it is running, all because I did the step by step methods told to me from here.

 

[tedious]

Re: Johnson 70 1986 stalling above idle

Flats, I have a 1989 70 with poor idle characteristics, pretty much the same as what you have. My feeling matches yours, that it seems like it's not getting enough fuel. Based on a recommendation I got here on iboats, I have replaced the idle air bleed orifices with orifices two sizes smaller, to richen up the idle mixture. Unfortunately, I will not get a chance to run the boat for at least a couple of months, when the snow melts.

I will try to find the other post that made the recommendation; unfortunately, I can't get the search function to work right now.

Tim

 

[tedious]

Re: Johnson 70 1986 stalling above idle

I see that I already made that suggestion in your other thread here: http://forums.iboats.com/showthread.php?t=372666 At the time, you were thinking your motor was flooding.

One way to check that out is to pull the plugs right after it stalls out - if you're flooding, they will be wet with fuel.

Tim

 

[SparkieBoat]

Re: Johnson 70 1986 stalling above idle

also could be the idle mixture screws...they should be about 2 1/2 turns out from a SOFT set..then you can make 1/4 turn adjustments either way and try running it for a few minuets, see if it gets better or worse, be sure to run it for a few minuets before adjusting again. also in the top of your carbs is a plate and gasket..when cleaning carbs make sure this area is all clean. also you can check your idle screws to make sure they are not "shanked" as a result of over tightening...if coils and plugs are good this would be my next thing. You never know who may have been turning these screws. They should all be set the exact same.

 

[tedious]

Re: Johnson 70 1986 stalling above idle

Not sure about Australia, but in the US the OMC 70 didn't have idle screws until the second half of 1989 - before that you need to swap idle air bleed orifices.

Tim

 

[skiers5]

Re: Johnson 70 1986 stalling above idle

Well fellas time for an update. Now have it ideling in neautral at about 1300 rpm, about 800 in gear, changes into gears and accellerates but bogs down.Results were achievd while in a test tank. I believe since I have played with things the throttle pick up point still needs to be adjusted on the cam lobe. I think at this point I'll save the money and take it to a marine tech who knows exactly what they are doing. I believe it can't be far from being sorted out. Does the rpm in gear and rpm in idle sound correct ?
Dean