Where to start with diagnosis.

[caretaker1]

This may be long, but here goes. My outboard is a 1996 Johnson 90 V4 model J90TLED. The engine will start and run on a dime every single time. The problem really is the fact that is smokes a lot more than I think it should and it sounds like it has a skip in it, you can def. hear the skip in it when the rpms are ran up. Here is what I have tested so far:
Compression-lowest 125
highest 133

I disconnected the VRO and ran the engine on an auxiliary tank with 50:1 premix and the problem did not go away.

I ran the "decarb" procedure through with the deep creep and seafoam in the fuel.

I changed every plug and gaped them at .030. The old plugs had a lot of oil on them but apparently not enough to foul out. I also pulled each wire while the engine was running and there seemed to be a pretty consistent change in the sound of the engine.

I am very mechanically inclined, but no little to nothing about outboards. My suspicions are that one of the plugs (or more) is not firing every now and then and then when it does, it burns all the extra fuel/oil mixture, but not completely, therefore the smoke. My question is where to start trying to find the culprit. Could it be something with the carbs causing too much oil to be in the fuel, or could it be an ignition issue? Thanks for the time, i'm new to boats, but look forward to a long life on the water.

 

[Daviet]

Re: Where to start with diagnosis.

Did you hook the VRO back up or are you still running it on premix?
Smoke is from the oil in the fuel mixture, the more oil the more smoke.
Some oils smoke more than others.

 

[caretaker1]

Re: Where to start with diagnosis.

Did you hook the VRO back up or are you still running it on premix?
Smoke is from the oil in the fuel mixture, the more oil the more smoke.
Some oils smoke more than others.

Its still running on pre-mix now, but the skip is there either way. The smoke does not concern me as much as the skip does.

 

[SparkieBoat]

Re: Where to start with diagnosis.

skip may be a weak coil possibly..bad plug wire, I would DVA test every electronic component.

 

[boobie]

Re: Where to start with diagnosis.

Hook up a timing lite to each cyl one at a time and run it. Turn the timing lite around and look into it. When ever you see any black spots, that's the cyl that's misfiring.