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Johnson 9.9/15 misfire

AMelbye

New member
Hi,

I have a 9.9 johnson/evinrude that I can't get to run right. It's a 9.9 with a dealer installed 15hp carb upgrade.

Here's a video:
https://www.youtube.com/watch?v=1SXqXq3dkAo

as you can see it will idle OK (perhaps a little rough), but as I try to up the RPM it will miss.

I've just had the carb apart, and it looks brand new. I let it soak a bit in brake cleaner and blew compressed air through every passage, but I don't think the carb is my problem, and it certainly did not help.

Since new the engine has always been a bit rough when cold, but smooth as soon as I got it properly warm.

In the last few year however I've had 2 or 3 times when it would suddenly stall for no apparent reason, in a big cloud of smoke, typically when I was giving full throttle. And not to start again for hours. Then it would for no apparent reason be fine again.

I just had the carb apart and it looks good as new. I've tried a different tank, and still I'm getting misfire like in the video. When I was about to use it this summer I managed to start the engine, but could not keep it running. I've measured compression a couple years ago and the top cylinder was about 50% down (cold engine). However I have had it running smoothly since then, so I'm finding this quite confusing.

What's wrong with this thing?
 
There is a mark on the throttle cam line the mark up center of the follower roller at that point the carb should be fully closed and just begin to open the carb butterfly as it passes center of the follower roller.
 
That snorting toward the end when you revved it up a bit is a lean sneeze. Check your spark/carb sync. But I think I heard a bit of ignition miss toward the earlier part. Have you tried some new plugs?
 
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