Johnson 140 Sputters at Full Throttle

[blakecox2015]

1992 Johnson 140hp (Model #: J140TXETF). Seems to run fine until pushed to full throttle and then it sputters. Doesn’t sputter until at almost full throttle. Just serviced same day and first time taking on the water since that it does this. Spark plugs replaced, new coil just replaced, new fuel filter. Checked all of the wires to confirm they were clean and fully seated. Compression test is good at about 90 on all 4 cylinders.

I attached a brief video showing from basically idling and going into full throttle. At the end you can hear it sputter and lose the power it built up. That’s what it does every time we throttle up. Don’t know the RPMs because tachometer is broke.
View attachment Video.mov

 

[jimmbo]

Seems awfully slow at Accelerating, or are you just slowing pushing the lever?
What are the Compression Numbers?
Does it has a Spark strong enough to jump a 3/8" gap at ally Cylinders?
Are all the Carbs getting Fuel and are Clean
Is the Timing set to spec, and the Carbs synced to each other and to the Spark Timing, and opening fully?

 

[stresspoint]

possibly someone messed with the high speed timing screw , in which case you need to get them to mess with it again with the motor WOT or close to it under load and set to spec with a timing light.
do yourself a favor , if the top end timing is out avoid running WOT till it is corrected.
it always has me bewildered why people have to turn screws on outboards just because they are there.

 

[racerone]

Hook up a timing light.----Just 1 cylinder at a time.----See how spark behaved as you throttle up.----Just observe the flashing light.