Johnson 90hp (J90PLEEB) issues
 

Last season I had purchased a boat and up to last past Friday, the motor Johnson 90hp (J90PLEEB) has run very smoothly and strong. On Friday, I was about 7 miles out, had stopped to do some fishing off the Island of Sholes and the motor did not want to start and when it did, the motor ran very rough, sounded like 1 to 2 cylinders were not firing. I should mention that on my way out, the ocean was glass and I was able to maintain ~22mph for the whole 7 miles.

Before pulling the boat from the water, I shot some decarb spray in each intake and you could hear the motor rev higher and the excess smoke. However, when flushing the motor, it continued to sound like 1 to 2 cylinders were not firing.

Yesterday, I had started up the motor, let it warm up and then pulled the plugs and tested the compression. All cylinders were right around 90 psi, which is the same as when I had purchased the boat last season. I then reconnected the plugs and started to pull 1 plug at a time to see how the motor responded.



Pulled bottom right cylinder plug and the motor had no change. However, you could hear there is a spark.
Pulled the top right cylinder plug and the motor would die.
Pulled the top left cylinder plug and the motor idle lowered.
Pulled the bottom left cylinder plug and the motor idle lowered.

While I ordered the carb rebuild kits and 4 new bowls, will clean/rebuild when they arrive.

Should I be looking at the power packs or something else?

I have added photos of the spark plugs, how do they look? These were installed in June and the boat has been used 12 times.

Video of the motor running

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Plugs look ok to me, but it’s either spark or fuel delivery..

Try a spray bottle with gas , shot into each carb and see if it picks up the dead cylinders.

Then try disconnecting the wires without a rag or pliers, you’ll know if a boot is leaking spark right away. Ha ha.

I would replace wires and plugs before digging in to carbs if above test with fuel shows nothing.

My wires were bad , same setup. Clean up the coils electrodes and dielectric grease inside the boots only.

Good wires will CLICK when installed . Tired ones will not.

Would not be a bad idea to remove the coils and clean and check the bolts and mating surfaces that holds them on to the block.
That is the grounding source.

Yup, felt that with the rag for the bottom right cylinder... it was a slight tingle.

That wire is bad then, leaking spark .
Replace the wires.
With OMC . NOT AUTO Store.

Johnson Ignition System Parts for 1999 90hp J90PLEEB Outboard Motor

Omc only for me.

And only Champion spark plugs will work properly on that engine , nothing else will do. It matters greatly.

Champion QL78YC - Champion Spark Plug ( #938M)

Ok... need to update the original post.

i can pull both bottom spark plug wires and the motor does not change. So I switched the coils top to bottom with the same result.

I then tested for spark (video to be posted) and each plug has spark, not sure if the spark is solid or often enough.

Last, I shot decarb into each throttle body and the motor did rev for each cylinder.

Recap... top plugs will cause the motor to change idle speed, bottom 2 had no difference. Switched coils and had the same outcome.

I also covered each Throttlebody with my have and gas did puddle up and the motor did bog down for each cylinder.

Compression was ~90 psi

powerpack has a date of 2016

Thoughts?

Reason carb not cleaned yet?
You don't need a rebuild kit to clean a carburetor.
You need a rebuild kit to replace parts
Ideal you should replace the bowl gasket when you clean it but many many many times you can just reuse it if you you're careful about it

If no fuel equals no oil.....quit screwing with motor until carbs is cleaned

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Rebuild kit/new bowls have on order.

Are you thinking a carb issue?

Read last sentence above
its a 2 stroke
How is it getting oil

Are your plugs Champions? Simple question.
It will not run right if not.

From my manual.
“The use of non suppression plugs will cause ignition problems”

Sorry, was reading the thread on my phone.

Got it...

I’m not going to claim to be a boat mechanic but I do tinker.
I don’t think it’s a good idea to spray the throttle body cleaner in while it’s running. It doesn’t have any oil in it. My can says do NOT spray while equipment is energized. A spray bottle with some premix in works great. Good luck!

And I agree... However, I am using the omc engine-tuner decarb spray (https://www.wholesalemarine.com/john...c-engine-tuner), which according to the instructions is sprayed while the motor is running.

Yup, Champions and they match what is suggested on the back of the power pack.


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Get some denatured alcohol and clean the optical eye sensor.
B

Id simply insure your getting fuel/oil to lower cyls before continuing running tests

What happens if engage primer? That squirts fuel directly into carbs.

Are you talking about the primer fuel gas line bulb or when you push the key in?

I think he is talking about the primer solenoid, which is when you push the key in...

When I press the key in, you do hear the solenoid activate.

I didn't check to see how much if any, fuel squirted in the carbs. However, with the primer engaged, the motor will start right up.