1966 Johnson 20hp won’t idle and makes a stutter sound

[Joem20]

Hey there, I have a 1966 Johnson FD-20 I got it not running and I got it running through new coils and a carb clean. But it still didn’t like to idle at all. So I rebuilt the carb and that helped. It now idles somewhat okay at low rpms but it dies a lot at idle. When I shift if I turn the throttle to the shift position it dies so I have to force it into gear at a higher rpm which can’t be good for it. The other issue is when it’s running there is a loud shutter and jolt it makes pretty consistently every 30 seconds, no matter the speed. Sometimes it does it every 10 seconds sometimes it does it once a minute. I attached a video of the shutter and jolt it makes. It runs good at full throttle but at idle it’s bad.

I would love to get some advice on this.

Thanks
View attachment IMG_0801.mov
View attachment IMG_0801.mov

 

[racerone]

Your video is not clear.----Have you opened up the slow speed needle to get rid of possible lean sneeze?----Checked gear shift adjustment ?----Possible jumping in and out of gear.----Throttle plate opening too early will make them stall out as well.

 

[Joem20]

Your video is not clear.----Have you opened up the slow speed needle to get rid of possible lean sneeze?----Checked gear shift adjustment ?----Possible jumping in and out of gear.----Throttle plate opening too early will make them stall out as well.

The stutter happens once in the video in the first few seconds you can see the motor jump or jolt then goes back to normal. I have tweaked with the carb needles a lot and have not found that to fix the issue. I don’t think it’s jumping out of gear but it could be. How would I check that

 

[racerone]

You don't think it is jumping out of gear !----But it is a common issue on them.----I can not touch your motor.----Up to you to do some inspection.----Lower units are elegantly simple to inspect.

 

[Joem20]

You don't think it is jumping out of gear !----But it is a common issue on them.----I can not touch your motor.----Up to you to do some inspection.----Lower units are elegantly simple to inspect.

What would I look for in the lower unit, broken gears? I’ve rebuilt the lower unit and all the gears looked to be in good condition.

 

[racerone]

Sorry------I missed the part about the rebuilt lower unit in post #1 .----I worked on these motors over 50 years ago.----They are easy to repair / get running properly.

 

[Nordin]

From the video it looks like it is jumping out of gear.

 

[Joem20]

W

From the video it looks like it is jumping out of gear.

What should I look at for the cause of that issue? Also is it a major issue that can cause damage or leave me stranded?

 

[Nordin]

I think on those engines you can not adjust the shift shaft.
The shift shaft has a coupler under a cover at the mid leg. Both shift shaft lower and shift shaft intermidiate has a grove where a screw will secure the coupling.
If the teeth at the clutch dog or the teeth for clutch dog at forward gear are worn it will slip under load.

 

[racerone]

The shift can be adjusted up top.

 

[flyingscott]

that looks like a miss either carb or electrical. run a timing light on it