running on one cylinder

[troutstalker2]

I friend gave me a 1986 25 hp johnson ducks unlimited edition motor, took it out for a spin and running great and after about ten minutes it died. I was able to start it but was bogging very badly. Did a compression check, about 105 in both cylinders. I started it at home and there was spark to both cylinders. I removed the plug wire from the top cylinder with no change to the running of the motor. Replaced the top plug wire and removed the bottom and it dies immediatly. I guess its running on the bottom cylinder only. the motor has not been run for four years. Were do I go from here?

Any help will be appreciated, David

 

[HighTrim]

Re: running on one cylinder

Start by swapping the coils. If the no spark problem follows the coil to the other cylinder, replace the coil. If not, we need to dig further.

 

[troutstalker2]

Re: running on one cylinder

There seems to be strong spark coming from both coils.

David

 

[mucduc]

Re: running on one cylinder

my 85 50hp didnt have spark to the top cylinder either but when i was swapping the plugs and cables between the top and bottom cylinders, both had spark. so the only thing i could think of was that there was bad connection to the top coil and the top wire. so when i put them back in their places i made a good connection.

 

[troutstalker2]

Re: running on one cylinder

I am getting spark through both wires from the coils to the plugs. The thing I don't understand is if I'm getting spark to both cylinders, why is only the botton cylinder fuctioning. My only guess is that it must be a fuel delivery problem, but that seems odd since both cylinders share the same carb. I'm a novice at outboard engine repair, I got this far and I'm kinda stumped.

David

 

[Daviet]

Re: running on one cylinder

Is your fuel pump pulsed off of the top cylinder?
Maybe you have a defective fuel pump and flooding out the top cylinder.
Just thinking.

 

[bankerjohn]

Re: running on one cylinder

How did you check the spark to each plug?

Have you tried swapping the plugs (or installing new ones)? It's possible that one plug is bad!