1994 Johnson 70 HP Stalls, after a minute on idle

[moxieman]

Okay, here is my problem. My 1994 70 HP will idle fine. Eventually though it will stall. It usually takes it about a minute for it to stall. I can barely even put the motor into gear with out it stalling either. I ran a compression check earlier this afternoon, all 3 were at 120. I also installed new NGK plugs. The motor runs fine at high throttle, no problems, but as soon as brought down to lower speeds it will stall out. Anybody?

 

[kenmyfam]

Re: 1994 Johnson 70 HP Stalls, after a minute on idle

Champion plugs and a carb re-build.

 

[kenmyfam]

Re: 1994 Johnson 70 HP Stalls, after a minute on idle

How was it before the NGK plugs ???

 

[moxieman]

Re: 1994 Johnson 70 HP Stalls, after a minute on idle

I just got the boat, and put the new plugs in. So I have no clue...

 

[kenmyfam]

Re: 1994 Johnson 70 HP Stalls, after a minute on idle

Should do a quick health check on the motor.
Compression and spark.
Post back back your findings.
Carb clean and a link and sync but that is a guess at this time.

 

[ob]

Re: 1994 Johnson 70 HP Stalls, after a minute on idle

Each carburetor on that engine should have an adjustable slow speed needle valve on the starboard side.Try seating (closing)one of them clockwise and count the exact turns it takes to seat it. Each engine will have it's own sweet spot somewhere between 2 1/2 - 3 turns open(counterclockwise).My 96' performs best at 3 turns open.

You need to install a new set of QL77JC4 Champion plugs in that engine gapped at .030".

 

[HybridMX6]

Re: 1994 Johnson 70 HP Stalls, after a minute on idle

Agreed, just sounds like a poorly adjusted idle screw to me, on all 3 carbs. My 55hp was the same way, it would die on me if I idle. I did as recommended on the board here, and no more problem. You have to do it in the water though, there won't be ebough back pressure on the system running on muffs to set it correctly.

 

[Silvertip]

Re: 1994 Johnson 70 HP Stalls, after a minute on idle

Idle speed and idle mixture work in unison. If idle speed is too slow, messing with the mixture won't fix that. If idle mixture is wrong, setting up the idle speed to compensate fixes nothing. Each time idle mixture is reset, so must the the idle speed. But gunked up carbs will not be fixed by simple adjustments. If rebuilds have never been done, they are long overdue.

 

[kenmyfam]

Re: 1994 Johnson 70 HP Stalls, after a minute on idle

Idle speed and idle mixture work in unison. If idle speed is too slow, messing with the mixture won't fix that. If idle mixture is wrong, setting up the idle speed to compensate fixes nothing. Each time idle mixture is reset, so must the the idle speed. But gunked up carbs will not be fixed by simple adjustments. If rebuilds have never been done, they are long overdue.

100% agree as per post #2 If in doubt, clean em out !!!

 

[moxieman]

Re: 1994 Johnson 70 HP Stalls, after a minute on idle

Now, what is exactly involved in doing the carbs? just drop the bowl? Clean with carb and choke cleaner?