Re: Johnson 25 jumps out of gear

[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.