Johnson 55 only running on 1 cylinder

[weekendfisher]

Hi Guys,
This is my first post on this forum i have had a look around and there is a ton of helpful information so i was hoping someone could help me out with my problem.

I have a 1994 Johnson commercial 2cyl 55Hp which seemed to be performing very poorly last time i went out.
Today i thought i should do a few tests and see what was up

Tested the compression and got 140 on top cylinder and 137 on the bottom cylinder so that seemed ok.
I then moved to checking spark both plugs are firing so i guess the coil is ok.

There is oil/fuel in the chamber and the plug is getting wet so i dont think it is a fuel problem.

If i take the bottom plug off when the engine is running there is no change however if i remove the top plug the motor cuts out.
If anyone can offer advice to where i should be looking next i would really appreciate it
Thanks

 

[Tim Frank]

Re: Johnson 55 only running on 1 cylinder

Check spark with a spark tester.

 

[tashasdaddy]

Re: Johnson 55 only running on 1 cylinder

replace bottom coil.

 

[HybridMX6]

Re: Johnson 55 only running on 1 cylinder

I have the same engine, just a 2000 model, and mine was doing this for a while. It only did it at idle though, so I cleaned and rebuilt the carbs and replaced all fuel lines, and the problem went away. If yours is doing it all the time, and pulling that bottom plug wire does nothing to affect how the engine is running, then the engine is only running on the top cylinder, and you need to find out why.
As instructed above, buy an adjustable spark tester from an auto parts store and then re-test the spark. From what I have learned on here, it should be able to jump a 7/16" gap with a strong blue spark. If not, it won't be strong enough to ignite the mix in the chamber, hence why it would be running on 1 cylinder.

 

[weekendfisher]

Re: Johnson 55 only running on 1 cylinder

Thanks for the advice guys.
The coil is the single type unit so it is harder to swap the coils to test them.
I will get a spark tester and see if it is caused by a weak spark during the week sometime.
Hope thats all it is
Cheers

 

[weekendfisher]

Re: Johnson 55 only running on 1 cylinder

Hi,
thanks for the help thought i would update on what the problem was.
Turns out the bottom carb is not getting fuel through so i am having both carbs rebuilt and a full service while i am at it.
Thanks again
cheers

 

[kenmyfam]

Re: Johnson 55 only running on 1 cylinder

Still need to check spark properly before thinking this issue is completely solved.

 

[HybridMX6]

Re: Johnson 55 only running on 1 cylinder

Still need to check spark properly before thinking this issue is completely solved.

Agreed. It's worth the $10 for the tool at the local auto parts store. I had checked mine before rebuilding my carbs, and found spark was good, which left me with not enough fuel getting in. Pulled carbs, bottom one had some gunk in it. Once cleaned and rebuilt, all works great.
I'd suggest you also check your spark, like I said, worth the $10.

 

[weekendfisher]

Re: Johnson 55 only running on 1 cylinder

Thanks for the advice,
The spark was checked before the carbs were deemed to be the problem.
I had a boat mechanic who i had dealt with in the past come out and check it over since marine motors a new to me and i didn't have a spark tester i though it best to let a professional look it over.
He was happy with the compression spark just said there was no fuel getting in through the carbs.
The rebuilt carbs are going back on tomorrow so i will see how it all goes.
I was also plesantly surprised to find i was not a 93 model as first thought but a 95 model.
Cheers

 

[weekendfisher]

Re: Johnson 55 only running on 1 cylinder

Just to let everyone know the final outcome
The freshly rebuilt carbs went on today along with new plugs fuel lines and gearbox oil just for good measure she now starts first go with both cylinders firing.
Glad to be able to get back into the water and thanks again to everyone who contributed
Cheers