150 only fires on 3 of 6 cylinders

[GunnerO]

My Johnson 150 Faststrike (1994, J150GLERA) is only firing on half it's cylinders. After this problem first started I changed the power pack - didn't help. I also disconnected the shift switch - didn't help. Checked the compression in all 6 cylinders - all good. Checked the spark - 1 side was good, the other had nothing.

I really thought the new power pack would solve the problem. I'm not much of a boat mechanic and I'm out of ideas. Anyone ever heard of this problem. Or better yet, anyone know how to fix it?

 

[boobie]

Re: 150 only fires on 3 of 6 cylinders

Could be a bad stator. Two seperate circuits, one for each side. Or bad connections.

 

[cfauvel]

Re: 150 only fires on 3 of 6 cylinders

Timer base is anotherr option as culprit, but I agree with Boobie, most likely the stator. Get yourself the tools to diagnose the problem before spending more money with guesses.

 

[boobie]

Re: 150 only fires on 3 of 6 cylinders

Sorry but no timer base on that mtr. It has an OIS sensor. Agree with cfauvel, you could use proper meters and an OEM service manual. The manual will be good for future use. Stay away from Seloc or Clymer.

 

[Chris1956]

Re: 150 only fires on 3 of 6 cylinders

Check the overheat sensor on the heads. Disconnect them and see if spark returns.

 

[boobie]

Re: 150 only fires on 3 of 6 cylinders

I'm curious. What do the overheat sensors have to do with no spark??

 

[Chris1956]

Re: 150 only fires on 3 of 6 cylinders

Overheat sensor will activate S.L.O.W. system, which kills spark to 3 cylinders.

 

[cfauvel]

Re: 150 only fires on 3 of 6 cylinders

Overheat sensor will activate S.L.O.W. system, which kills spark to 3 cylinders.

Not sure if anyone mentioned this either, but a stuck shift assist switch will kill 3 cylinders on the starboard side...what side is dead?

 

[boobie]

Re: 150 only fires on 3 of 6 cylinders

When SLOW is activevated it stumbles ALL the cylinders above 2500 rpm. Below 2500 rpm the mtr runs normal even tho' the overheat horn is blowing from being tripped by the overheat sensor.

 

[aerobat]

Re: 150 only fires on 3 of 6 cylinders

i am not sure, but i also dont think SLOW cuts 3 cylinders on one bank. imagine the roughness respective the running possibilty of the engine. it due to my knowledge slows all cylinders.