25 HP Johnson won't idle. I need help!

[sr522re]

I have a 16ft Deep V with a 25 HP Johnson (Model # TJ25ELCEB). The motor was running great earlier this year. I typically have myself and maybe one other person in the boat with me and the boat will do about 20 mph. A week ago I took one extra person with us so 3 grown men in the boat. The boat took a bit to get on plain, and once it did we could top out around 16 mph. About 5 minutes into the ride the motor just felt like it was getting tired. We maintained plain, but the boat slowed down a bit. When we reached our destination I started to throttle down and the motor just quit. About 3 hours of fishing later we needed to start the motor back up and head back to the boat launch. The motor would not idle at all. I had to start the motor near full throttle and back off and shift into gear as soon as possible and then back to full throttle to get the motor to stay running. Again the boat would get on plain and was able to get us back to the boat launch. About 50 ft. from the launch I throttled down and the motor died again. It will not run at anything less than half throttle.

This past weekend I started to diagnose the problem with no luck. Here are some facts that I know and things that I have checked.

The plugs looked good
I have 110 psi compression in each cylinder ( 2 cylinders)
I took the carb apart and cleaned it thoroughly. Didn't need it though.
I checked all the carb linkages per my service manual and everything is adjusted properly.
I checked and adjusted the timing per "Joe Reeves Timing Procedure".
My fuel line and primer ball function properly. No leaks and the ball is solid once primed.
My slow speed needed is adjusted at 1 3/4 out per manual.
Currently the motor will run great at high RPM on muffs. It will not run at idle or about anything below half throttle.
I have messed with the throttle cable and even removed to eliminate it as a variable.

I am truly stumped at this point and don't know where else to look. If anyone has any advice or suggestions for me to try I am open to anything. I really appreciate the help and look forward to any and all comments.

Thank you,

Chris

 

[F_R]

1. Don't be running it at high RPM on the muffs unless you want to scatter parts on the lawn.
2. Check to make sure it is running on both cylinders

 

[sr522re]

It wasn't intentional. It just lit up when I started it and I backed it down right away. Again, I can't get it to start in a neutral position. I have to increase the throttle for it to run. I can get the motor to come close to an idle speed (around 1000 rpms), but the throttle is still near half (butterfly is about half open at this point). Anything close to neutral will kill the motor instantly. Thanks

 

[oldboat1]

Just a wild guess -- check the vertical throttle tower on the side of the powerhead (throttle side). It's called the throttle lever and pin assembly on your model. It's possible the throttle linkage up there is broken, giving loss of control. Try moving the throttle plate by hand, keeping an eye on all linkages.

 

[kbait]

Make sure spark will jump1/4" in open air from both plug leads. If that's good, use a timing light to see if it's firing at the right time, as your motor has under flywheel ignition (UFI) that combines the functions of regular CDI box (exterior mount) and sensor coil ("trigger" under flywheel). With UFI, you could have good spark, at the wrong time.. I've only seen that once..replaced UFI and then it ran correctly. Oh, and make sure flywheel key is intact..that'll throw off timing too.

 

[sr522re]

If it helps, I took a short video of the motor running and some of it's symptoms. There is also a quick "walk around" of the motor so you guys know what you are looking at. In the video when I am able to get the motor to run at about 1000 rpm's the throttle is about half throttle. One little nudge of the throttle and the motor wants to rev really high. Check it out and let me know what you think. https://youtu.be/OBNGG5qfrO0

Thanks,

 

[interalian]

Looks like your timer base is rubbing and catching on the flywheel. It should only move with the throttle.

 

[sr522re]

Interesting. Yeah, it definitely jumps around a bit. Is that keyed I wonder?

 

[interalian]

You have a power pack, stator, charge coil etc on an ignition plate under the flywheel. Something could be loose or worn, rubbing on the flywheel. Or the throttle linkage is loose/damaged/missing parts.

Edit: see post #4 - oldboat1 may have nailed it

 

[sr522re]

Getting closer... check out this second video.

https://youtu.be/nnEqMmXp5GQ


So this time, at full throttle, I disconnected the carburetor linkage from the timing cam arm and started the engine. With the carb at an idle position the motor idled well. With my hand pulling on the carb link I could rev the engine as normal. Keep in mind my throttle is still at full throttle. As soon as I back off on the throttle the motor dies again. So does this narrow it down to timing? All the throttle cable and linkage seems to be fine. I don't see anything lose or broken. Please let me know what you think. I really appreciate all the input.

Thank you all!

Chris

 

[oldboat1]

Well, your remote throttle lever appears to be wide open, as you indicate, while the motor throttle is not. Additionally, your motor is in neutral while the remote lever would indicate the motor should be in forward gear. (I'm assuming the remote lever would not advance that far at fast idle/neutral warmup, but might be wrong.)

You need to disconnect both the remote throttle and shift cables at the engine, then troubleshoot. With the motor turned off, manually return the throttle to idle, rotating the the throttle plate by hand if you have to. Then check the shift for operation using the lever at the motor. I think you should see a lockout mechanism blocking throttle advance unless the motor is in gear -- not seeing it, but maybe because I'm not very familiar with your motor. (With the motor off, you may need to rotate the prop a little by hand to get the gears to mesh when shifting.)

You may find the problem is with the cable box or cables, although you should first make sure the motor operation is as it should be -- then fit or refit the cables to the motor. Test remote cable operation while the cables are still disconnected -- lever should move easily, and travel for both cables should be smooth. I suspect you have a problem at the cable box or the motor would be shifting remotely (assume it isn't). It's possible you tried to force the remote lever, and broke part of the mechanism in the box (I did that this Spring.) But again, work on the motor first.

(Want to be careful about revving when on muffs, btw, as was suggested earlier.)

 

[sr522re]

Yes, the remote throttle was wide open, and as far as I could tell the motor was as well. At the remote throttle box I am able to pull out on the throttle keeping the motor in a neutral position. It does not appear to limit the rpm's at all in this neutral position. With the cables disconnected from the motor the remote cable box is silky smooth and seems to be fully functional. No issues there as far as I can tell. I will definitely take a closer look to see if manually shifting the motor into gear has any effect on the way the motor runs. I also plan to pull the flywheel this weekend to see if the key is worn out creating unnecessary slop. Definitely some good suggestions to look for. Thank you all for the time and input. I really appreciate it!

 

[interalian]

There's a thread on the front page for an '88 model 25 showing how it's idling. If you look at how his timer plate sits while idling you'll see what it should be doing. Around the 18 second mark, the revs are being brought up and the timer plate moves as it should to increase motor speed.

https://www.youtube.com/watch?v=h8-bSpJU0wA

And as oldboat1 says, if your control is at full throttle and your shift is in neutral as seen in your video, something isn't right on the shift side.

 

[sr522re]

Update: I finally removed the flywheel to see what was underneath. Everything looked pretty dirty and I found a loose part. See link for another video.


https://youtu.be/O6IJ3aFZXUc


Again, all the linkage for throttle seems very smooth. It's actually a lot smoother without the flywheel attached. I'm not sure if that's normal or not. My bigger concern is this lose part. Does anyone think this would effect my timing with throttle at an idle position as I originally posted? Please take a look at the video and if anyone sees anything I should check or do please let me know.

Thanks so much guys! I really appreciate it.

Chris

 

[AlTn]

yes that loose part would have an effect as it's being struck by the flywheel magnets, tighten it back down and make certain that all the coil faces and heels do not extend beyond the bosses on the armature plate < they should be flush with each boss >...I'd try to get as much aluminum off each coil face and heel as possible as well...what does the inside of the flywheel look like?...smooth up the areas covering the magnets before trying to reinstall it

 

[sr522re]

Fixed! I hope... I tightened down all loose electrical components and cleaned with Emery cloth. Inside of flywheel was pretty dirty as well so it also got cleaned. Reinstalled the flywheel and hooked up all carburetor linkages. Motor now runs at idle and revs as it should. Hoping to get it back on the water some evening this week to test it out.

A big thanks to everyone here for helping out. All suggestions helped me learn and fix my issue. Thanks so much!

Chris

 

[interalian]

Yup, that'll do it. Glad you figured it out.