1987 Johnson 120

trying to troubleshoot my 1987 Johnson 120 Outboard. There has been quite a bit of work done too it recently but it's still having issues with one or two cylinders.

[@markkellycichosz8534]

I pulled my 1987 apart and the reed valves were all slightly open. Started as bad as yours did. Now it starts fine.

[@andydavidson9707]

Did you ever figure out what was going on with this? I've got a 86 120 that runs rough too and came across your video in my searching for an answer.

[@jordansilva4498]

Did you ever find a fix im dealing with this right now. It has no spark going to the upper right coil pack running on three cylinders

[@silverstarflite135]

I can here a cyl knock...have you done a compression check? Sounds like a cracked ring....

[@RedDragon72q]

I know it's been 7 years but did you ever fix this? I have one that is doing the exact same thing. Already cleaned the carbs to a spotless shine and all new gaskets. This is driving me crazy.

[@dougyfresh9013]

I have the same thing happening with mine. Can’t figure it out. Just put it in a shop today. Did you get yours figured?

[@RedDragon72q]

@@dougyfresh9013 Mine was the eight bolts behind the carbs that hold the butterfly plates on. The carbs attach to it. Two are bolts and two are nuts on each side. They were loose and allowing air in as well as gunk. I tightened them but that only helped so much. I pulled them off and cleaned up the area and replaced the gaskets. Once that was done and with clean carbs and new carb gaskets she runs without hiccups but the idle is high. I tried adjusting it down as much as I can but the stop won't go any further. At least she runs now and actually runs good.

[@dougyfresh9013]

@@RedDragon72q thanks for the info. I appreciate it.

[@ct1762]

@@dougyfresh9013 his issue here is the throttle plates are being held open just a tiny bit, allowing air in at idle causing it to sneeze and die. simply unscrew the cam roller set screw and I bet it smooths right out. this video was painful to watch IMHO.

[@dougyfresh9013]

@@ct1762 mine never got fixed. Shop couldn’t figure it out so I sold it.

[@captainedc]

I believe this is at least a 1988

[@ashleypatt3rsonpatterson523]

Top coil

[@silverstarflite135]

Well, your last test confirmed that its only running on three cyls. So its not a power pack which would had downed both the upper and lower cyl. I still say i hear a pretty noticable knock and rattle...I bet if you pulled off the head on that non firing cyl you would find a loose ring (or broken). The cyl is not firing.

[@Straitnet]

Alan..man that is a new possibility I hadn't heard mentioned before. I did a compression test, would that show a bad ring? If not..is pulling the head the only way? The last compression test I did showed 135 on all cylinders...but that was right after trying to run it. Before that it was like 125 on all. Also did you happen to see the other shorter video? After this video was done I cleaned out the jets in the carbs and got a new erratic idle when on muffs. Thank you.

[@GodBlessedAmerica]

Check the Timer base.

[@cgrobe21]

You should never run it without the air box on. It leans the mixture out and will ruin your engine. That's why its hard to get running.

[@cjsummer4403]

water pump bad takes to long to piss out

[@thomasflynn642]

omc junk!

[@captainedc]

One of the best outboards ever built