1990 70 hp Johnson missing at high rpm

WT2

Seaman Apprentice
Joined
Mar 4, 2009
Messages
41
I am trying to see if there is any constant problem with this motor and the electrical systems. It runs great at low rpm ,starts up fine and idles well but as I rev it up it starts to spit and sputter until I bring the RPM back down. Wonderign if it is a coil pack
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
38,451
Test run with a timing light.---That may find an ignition problem.-----Have you done a compression test ?
 

flyingscott

Fleet Admiral
Joined
Apr 8, 2014
Messages
8,152
Does your motor have S.L.O.W mode on it. Look at the powerpak and see if it has SL on it.
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
38,451
The 1990 models are equipped with S.L.O.W.--system---------Use timing light to see if you can find ignition problems.-
 

WT2

Seaman Apprentice
Joined
Mar 4, 2009
Messages
41
I will check with a timing light. I ran ohms on the coils they were all pretty consistent values. I did test a new one and the ohms were much higher. Also found one spark plug wire with some wonky values so I replaced it . each time I fiddle with it things get better but still not there. Hopefully the timing will tell me something but I have to wonder how does that ever change with out someone jacking with it. Also I will read up on the SLOW tech. Thanks.

I am planning on rebuilding the motor in the near future. I bought it from someone who stripped out the bolts that hold the motor to the frame which caused it to ware the crank splines. So each time I replace the drive shaft it only last a couple of years. Any thoughts on after market rebuild kits for this?

The compression test I did last year was very even all around 115, I believe. It was good enough for me not to worry too much about the compression
 
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