‘99 Johnson 90 running on 3 cylinders.. sort of

[cdembek]

I have a '99 Johnson 90 (J90PLEEB), compression is ~90 in all 4 cylinders, recently rebuilt/cleaned the carbs (3 times now), and replaced the starboard side reeds.

I have 2 issues that I am trying to solve.

1) Drop cylinder test - When pulling the starboard cylinder plug, the bottom cylinder does not change RPMs. However, if I cover up the air intake for that cylinder, the motor bogs down and stalls. When I pull the plug, I can see the plug is wet.

2) Using muffs or a bucket, the motor starts right up every time. However, the motor cuts out around 4 -5 mins. This seems like a fuel delivery issue.

I have zero issues bringing the boat/motor to a local shop, however, they are all 2-3 weeks out. I am located in York Maine, so that would kill what time I have left this summer. Also, I would like to learn how to be able to troubleshoot fix myself as I do have the tools to do so.

Also, when running the motor in a tub, should you see a build-up of oil on the front of the lower end? Assuming this is the 2 stroke oil out of the exhaust when running?


https://youtu.be/4cz-ZhLh5Bo
​​​​​​​

 

[James R]

If it is a fuel problem you can prove and isolate which cylinder it is. Mix 50:1 and put it in a spray bottle. Remove the air box.
Run the motor and shoot spray into the individual carb throats. If that cylinder dies then it is getting fuel if it picks up then it is not. If nothing happens then the fuel is not being burnt. Ok, now to check the sparks. Use a gap type tester for this. Each spark should be able to jump a gap at least a half inch hopefully more. From what you have said it is most likely a spark issue. Of course it could be lousy plugs.
Hope this helps.

 

[cdembek]

If it is a fuel problem you can prove and isolate which cylinder it is. Mix 50:1 and put it in a spray bottle. Remove the air box.
Run the motor and shoot spray into the individual carb throats. If that cylinder dies then it is getting fuel if it picks up then it is not. If nothing happens then the fuel is not being burnt. Ok, now to check the sparks. Use a gap type tester for this. Each spark should be able to jump a gap at least a half inch hopefully more. From what you have said it is most likely a spark issue. Of course it could be lousy plugs.
Hope this helps.

Thank you James for the suggestions.

Will have to try the spray bottle trick.

Plugs were new this season and have been swapped around to rule out. I have posted a photo of the plug and as you can see, the plug is wet.

Another test I did and I am not sure if it means anything, but I closed off each air intake and the offending cylinder did respond and bogged down. Now I am not sure if that means anything.

 

[cdembek]

Anyone?

 

[racerone]

Hook up a timing light.----Test run and see what happens when motor falters.------Test each plug lead.-------Oil injection in service and oil output tested ?-----Water pump impeller replaced.-------Vapor tank inspected and cleaned ?

 

[McGR]

Plug looks a bit wet. Maybe o-ring "head gasket"? Pretty cheap and easy to replace. Might be worth covering that base, check for spark then clean or replace the spark plugs.

 

[jakedaawg]

My bad...

 

[racerone]

Jake, Jake ----What nonsense are you talking about with carburetors on opposite cylinders !!!-----This is a 60 degree looper and NOT a 90 degree 120 / 130 / 140 looper !

 

[jakedaawg]

thanks racer...guess I read the thread wrong...I had 120 in my head while typing.