'90s 25hp Johnson jerks at idle

[gannet586]

The video offers the best explanation of what's happening. The motor starts up great, runs smoothly, pumps water strongly, with the exception of an occasional jerk. If you watch the video, it sounds like the fuel is getting cut for a second. Mostly the motor picks back up and continues running, but sometimes the jerk causes it to shut off entirely. Hoping for some direction in what to investigate here. The longer video shows the occasional jerk, and the shorter one is where I caught it shutting off entirely.

https://flic.kr/p/2sc7Uun

https://flic.kr/p/2sc7be8

 

[racerone]

Outboards have exhibited this CLASSIC " LEAN SNEEZE " since time began.----Try opening the low speed mixture screw 1/8th turn at a time.----Or post a picture / video of the stop screw on that thin rod on the port side of the motor.

 

[gannet586]

Ah, that makes sense! Thanks for the education and simple fix. I'll adjust that low speed mixture screw (#1). Is there a second screw to adjust..? #2 below has a plug of silicone caulking in it, but I had found one video of someone adjusting the screw there.

.

 

[racerone]

Need model number.----Get rid of silicone !---Post pictures again.

 

[gannet586]

Silcone b-gone! Model number is J25RLCEM.

 

[Droid]

#2 with silicone removed is your idle mixture screw. Like Racer said, 1/8th turn counterclockwise & let it idle & stabilize. On a warm engine.

#1 is an idle air bleed orifice not a mixture screw. Don't touch it.

Final adjustment must be made in the lake with the motor down sitting at its normal depth. And it may require more that 1/8th turn, that is a starting point.

1989 motor

 

[racerone]

The picture of the stop on the thin rod-is still missing !-----It can be so easy to help with information.-----I can not see / touch your motor !

 

[gannet586]

The picture of the stop on the thin rod-is still missing !-----It can be so easy to help with information.-----I can not see / touch your motor !

Thanks @Droid. Racer - help me out with which thin rod on the port side you're talking about, is it in these pics?

 

[racerone]

Correct.----I would say that you to open up the low speed mixture or clean the carburetor.

 

[timguy]

Make sure this o-ring #13 is good condition. I'm wondering about the


silicone?

 

[timguy]

Anything to do with gasoline exposure, adhive or sealers w/ silicone base should be avoided.
It won't last.

 

[gannet586]

Make sure this o-ring #13 is good condition. I'm wondering about the


silicone?View attachment 37064View attachment 37065

Good point, I assumed maybe an outboard mechanic had put it in there at some point to prevent the user changing the lean/rich mixture. But I suppose it also could have been a workaround for a broken o-ring like you say.