90HP Johnson with a Mis

M

Miroash

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I have 90Hp Johnson with a mis on the top Starboard side cylinder. When I pull the plug wire when its running it does not change the way it runs, this is how I know it is the cylinder doing it. It has 120psi compression and seems to have good spark. I have swapped the coil for one that I know works and it makes no difference. can the carb cause only one cylinder to mis? it seems like it is getting fuel.
 
countvlad

countvlad

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Re: 90HP Johnson with a Mis

Miroash said:
I have 90Hp Johnson with a mis on the top Starboard side cylinder. When I pull the plug wire when its running it does not change the way it runs, this is how I know it is the cylinder doing it. It has 120psi compression and seems to have good spark. I have swapped the coil for one that I know works and it makes no difference. can the carb cause only one cylinder to mis? it seems like it is getting fuel.
Click to expand...

puling the plug wire even if the cylinder is running corectly you wouldnt see/hear a diffrence.... leave the plug on that cylinder and pull the plug on a diffrent cylinder..... does it sound diffrent now? does it die?
 
M

Miroash

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Re: 90HP Johnson with a Mis

Yes. I pulled The wire off of all the cylinders and they all changed the way it runs with the exception of the top starboard cylinder which makes no difference whether it is on or off in effect the cylinder is dead (this is how I knew which cylinder the problem was in), except that it has spark and compression. I confirrmed compression with compression tester and I swapped coils from one of the other cylinders to eliminat spark as the problem. Any other suggestions? I am leaning toward carb but I do not know how to confirm it is the problem.
 
Silvertip

Silvertip

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Re: 90HP Johnson with a Mis

Remove the air silencer and give the engine a squirt of fuel/oil mix in the throat of the carb for the cylinder that's missing. If you have spark and compression, it should pick up. No starting fluid for this test!!!!!!!!!!!!
 
lostinboat

lostinboat

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Re: 90HP Johnson with a Mis

did you use a spark tester to check for spark or just swap coils???
 
M

Miroash

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Re: 90HP Johnson with a Mis

lostinboat said:
did you use a spark tester to check for spark or just swap coils???
Click to expand...

I did both. First I used a spark tester and it showed ok, but I swapped coils with one I knew worked just to confirm it was not a spark issue. so I am left thinking either a carb issue or maybe a bad power pack for that cylinder, since I connected the cioil to the same wires when I swapped coils so the powerpack connection did not change, so i might swap powerpacks and see if the problem moves. anyone think it is one more than the other?
 
M

Miroash

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Re: 90HP Johnson with a Mis

does anyone know if bad "Reeds" could cause this? I do not know what they are much less what they do. somebody mentioned them and I didnt even know there was such a thing. Does my engine have them, What are they, Where are they, and what do they do? could they cause one cylinder not to fire?
 
M

Miroash

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Joined
Jul 15, 2009
Messages
126
Re: 90HP Johnson with a Mis

Miroash said:
does anyone know if bad "Reeds" could cause this? I do not know what they are much less what they do. somebody mentioned them and I didnt even know there was such a thing. Does my engine have them, What are they, Where are they, and what do they do? could they cause one cylinder not to fire?
Click to expand...

???
 
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