Johnson 25 jumps out of gear

[old-wheezer]

72 Johnson 25 hp jumps out of gear and right back in again when accelerating. I checked the clutch dog, cradle and shift lever in the lower gear case and they all look good. The gears in the gear case also look good. What else could it be? Thanks for any and all suggestions.

[RICHARD A. WHITE]

The adjuster needs adjusting….it is the knurled wheel near the connector on the motor…. Basically the shift lever is not engaging enough/ not being pulled far enough forward…. rotate the wheel counter-clockwise looking at the front of the motor.. Does that make sense??? If the dog is good, then it probably is the adjustment..

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[billw]

Might want to send pics of the gears and clutch. It usually takes just a few jumps to make them look NOT good…

Long live American manufacturing!

[Casey Lynn]

quote Richard A. White:

The adjuster needs adjusting….it is the knurled wheel near the connector on the motor…. Basically the shift lever is not engaging enough/ not being pulled far enough forward…. rotate the wheel counter-clockwise looking at the front of the motor.. Does that make sense??? If the dog is good, then it probably is the adjustment..

This is a secondary adjustment. Only needed when a shift cable/control box is attached and not on a tiller only engine.

There is a primary adjustment at the shift lever on the engine. This should be accomplished regardless of tiller only or control box operated.
Behind the shift lever there is a screw and jam nut that attaches the actual horizontal shift shaft to the shift lever.
When adjusted properly and shifted into the detent you should feel an increase in drag on the prop when the prop is rotated back and forth.
Get a feel for what I am talking about with the gearcase in neutral then shift it into forward and pull the shift lever as far forward as you can. You should feel an increase.That increase is where the clutch dog is bottoming out against the forward gear dog and maximizing the adjustment.
To make your adjustment where you can feel this, the shift shaft, once loosened, needs to be rotated slightly rearward and snugged back up. Small increments at a time until the point that the extra drag is felt when the shift handle shifts into the normal spring loaded detent.

[dan-in-tn]

I agree with BillW that a few pics might be helpful in determining the fitness of the dog and gear. Assuming that they are OK, the shift lever can be adjusted as well as any shift cable that may be involved. It is important that when you push the shift lever forward in gear that you can feel the dog rub the forward gear. By rotating the propshaft back and forth you will be able to feel the face of the dog rubbing the face of the gear at the bottom of the engagement face. That may be a little hard to understand, but you are looking for as much engagement as you can accomplish. The shift lever is adjustable on its shaft to help you achieve this. If you get full engagement in forward gear and still jump, you have a gear/dog problem. Several on the site have talked about putting a negative two degree ramp on the dog and gear to help them lock/pull themselves together. It is important that both lugs pull together. Pappy has talked about this before. Maybe he will chime in again. Easily done on a milling machine with a degree head and smaller HP is not as critical. New gears are pretty expensive so you don’t have much to lose in giving it a try.

Dan in TN

[frankr]

That motor has the ball detents clutch dog. That is intended to ensure that the dog fully engages with the gear. Yes. it is true that external factors such as being out of adjustment can prevent that from happening. Tell ya what—many people tear those things down and say they look fine, when in fact they aren’t. It takes surprisingly little wear on the dog ears and gear recess to make it jump out. And every time it does that and slams back in, the wear quickly increases.

Bottom line is unless you find gross mal-adjustment, you need to go back in for a more critical look.

[fleetwin]

How did the driveshaft splines look when you had the gearcase off?

[old-wheezer]

Drive shaft splines also looked good to me. I will try adjusting the shift lever as recommended and see what happens. If it still jumps out of gear I will start over with a much closer look. Thanks guys!

[Casey Lynn]

quote t2stroke:

I agree with BillW that a few pics might be helpful in determining the fitness of the dog and gear. Assuming that they are OK, the shift lever can be adjusted as well as any shift cable that may be involved. It is important that when you push the shift lever forward in gear that you can feel the dog rub the forward gear. By rotating the propshaft back and forth you will be able to feel the face of the dog rubbing the face of the gear at the bottom of the engagement face. That may be a little hard to understand, but you are looking for as much engagement as you can accomplish. The shift lever is adjustable on its shaft to help you achieve this. If you get full engagement in forward gear and still jump, you have a gear/dog problem. Several on the site have talked about putting a negative two degree ramp on the dog and gear to help them lock/pull themselves together. It is important that both lugs pull together. Pappy has talked about this before. Maybe he will chime in again. Easily done on a milling machine with a degree head and smaller HP is not as critical. New gears are pretty expensive so you don’t have much to lose in giving it a try.

Dan in TN

Been there/done that on the undercuts and they work perfectly….every time. The undercut forces the gears together harder with every power increase.
Have used around 4 degrees. I can’t claim to be the first and got the idea from a Johnson dealer down in Avon Park Florida many years ago. He would take several sets of 18-25hp gears and clutch dogs to a local machine shop and have them all done at once to minimize set-up time. They used a full 4 degrees as well.
For do-it yourself guys this can also be accomplished by the use of a Dremel and simple stones. The stones have to be cut around 4 degrees or so. This will ruin a file but only a small portion at a time!
Leaving the part farthest away from the collet as the widest part. The stone is ground to the angle by using a file. The stone is then placed at the bottom face of the dog or gear and can begin cutting the bottom side of the dog face first and most to achieve the undercut. This is a longer process because fit has to be checked by the use of a marking compound. I have done this process on a couple of my personal gearcases and they have lasted well for years now. For customers I have had several sets done and they have been out and running without issue as well.
Yes Horace, the hardening is removed by either process but the undercut adds physical area to the dog face and therefore reduces overall loading.

[dan-in-tn]

Yes those were all the things I wanted to say without writing forever! Thanks everybody.

Dan in TN

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