1975 25hp Johnson 25R75B jumping out of gear.

Took the boat out for the 1st time this year with my "new" motor. Started up just fine, put it in forward, and off I went. Made it about 50 feet and the motor "kicked" and revved up. I realized then that it had kicked out of gear. So I put it in gear and took off again...made it about 20 feet and it did it again. It will go just fine at idle, but when I give it some throttle it will do a little kick and rev up.

I'm assuming it's in the lower unit...probably the clutch dog and forward gear?

Here is a video I took, sorry for the sound/quality all I had was my cell phone.

https://s2.photobucket.com/albums/y32/d_rednour05/?action=view&current=IMG_0328.mp4

I think you have an adjustment on your cam actuator that may help the problem your having?

Does it make a difference that the actual shift lever does not kick back?

It stays in the forward position and after it "kicks" I can apply a small amount of pressure and it will engage again.

I tried holding the shifter forward and it still did it.

You will have to go into the gearcase and repair. The clutch dog and forward gear have to be replaced at this point in most cases. On most models, in order to get the forward gear the pinion must be ordered as well as they come in a set. Yours may be different. There are some who will simply turn the clutch dog around and put the assembly back together. This buys you some time only.
The adjustment spoken of in the other post is a valid one when new parts have been installed. When the gear lever is in it's foreward gear detent you should feel the clutch dog bottoming out in the logs of the forward gear and creating additional drag when the propshaft is rotated back and forth by hand. If this is not felt you can adjust the shift assembly until the additional drag is felt and then lock it down.
I have been re-cutting the worn drive lugs successfully and adding an additional undercut of around 4-5 degrees. This effectively locks the dogs in place and is more effective as load increases. You are going through the case hardening but the undercut more than makes up for this. Cheap to do in comparison to gear and dog costs. You may be able to get a machinist in your area to do this for you.

So by doing a little research, the clutch dog and forward gear will run me in the ball park of $250?

Would I be better off trying to find a replacement lower unit?

I have been re-cutting the worn drive lugs successfully and adding an additional undercut of around 4-5 degrees. This effectively locks the dogs in place and is more effective as load increases. You are going through the case hardening but the undercut more than makes up for this. Cheap to do in comparison to gear and dog costs. You may be able to get a machinist in your area to do this for you.

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I have done this with a different twist.Sine I tig weld I just weld up the bad part & file it down.Good as new.

So for arguments sake, could I reverse everything just to keep me going until I get new gears or a diff lower unit?

baseball_guy_99 said:

So for arguments sake, could I reverse everything just to keep me going until I get new gears or a diff lower unit?

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if you look for a replacement part remember that in most cases it does not have to be from a 79 like yours. evinrude/johnson are the same motors and there should be a few years leway on what parts will match. cross reference the part numbers and you will be in good shape. i cant remember the site but if you pm me there is a great place in florida that has good used parts for a fraction of the cost of new parts....

Thanks for the info. My research shows me that the parts from a 71 through 76 will also work on my motor. I was in contact with a marine salvage yard a couple hours away from me and the guy said he has a good use lower unit. All that it's missing is the driveshaft. Which mine is in good condition so I can just use it. He said he would take $80 for it.

Well I pulled the lower unit completely apart this morning. Everything looked fine, but the gears all showed signs of wear. So I went ahead and ordered the replacement lower unit.

The place is only a couple of hours away so hopefully I'll get it tomorrow or Thursday.

I can't believe how easy and simple these motors are. I pulled the whole lower unit apart, cleaned it, and put back together in less than an hour.

Well I got the lower unit in today. Extremely fast shipping (he was only 2 hours from me).

Pulled the water pump and drive shaft off my old one and put it on the new one. It bolted right onto the motor just like he said it would. I then went to put the prop back on...well apparently the prop/nut combo that I had on the old LU won't work on this one. So I called up Josh (joshswatercraftrepair.com) and talked to him about it. Well it all boiled down to him sending me a cone for the prop which is originally what it was supposed to have.

So I'll put out a pitch for him...excellent guy and excellent service.

Josh's Auto & Watercraft
5201 Leach RD
Rochester, IL 62563
Fax: (217) 498-2083
Shop Phone: (217) 553-5157

Here is the new LU installed (i know its a different color but as of right now all i care about is it works!)

So long story short. The new lower unit prop shaft was too short. So I basically gutted the new
Lower unit that I bought. I took all the gears and everything out of that one and put it into mine. Took it back out to the lake today took off just fine but when I got to about three-quarter throttle it jumped out of gear again.

The only thing I didn't change was the shift fork, shift rod, and pinion gear.

One thing I did notice that when I shift from forward to neutral it doesn't always go right into neutral. I have to jiggle it a little.

Any thoughts?

If you would go back up to my earlier post you would see that the answer is already there. You needed to adjust to make sure the unit is going all the way into forward and that probably didn't happen.
But - let me throw you a get out of jail free card on this one and tell you that my statement is based on the assumption that the parts you purchased are capable of holding themselved in gear to begin with! If not then it would not matter whether you made the adjustment or not.

I went and re-read your post. I'm not sure what you mean by adjusting. Could you elaborate for me?

Pappy, are you talking about loosening the screws on the shift lever and adjusting the shift lever?

you replace the clutch dog?

I had a late 70s johnny 25 that did exactly as you described..and that was the culprit.

Not enough adjusting in the world to fix a worn clutch dog..

baseball_guy_99 said:

Pappy, are you talking about loosening the screws on the shift lever and adjusting the shift lever?

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i didnt read his post but would have to beleive thats what he meant. there should be 2 screws, make sure when you adjust it that it will go into forward and reverse fully. meaning theres a peice that has a rounded notch that the shifter sits in for forward and reverse, if it does not fully engage in both gears it will not perform like its suppose to....

I replaced the clutch dog with another used one that did look better than the one I took out.

I'll try the adjustment and if that doesn't work I guess I'll buck up and buy a new clutch dog and forward gear.

Yes that is what I meant. Play with the adjustment while rotating the prop back and forth until you feel the additional drag induced by the clutchdog fully bottoming out into the forward gear dogs. Make an adjustment and then keep one hand on the shift lever while rotating the prop back and forth and lightly force the shift handle farther forward and you should feel a difference between fully bottomed and not. Unfortunately there is no better way to explain this other than the common sense feel/experience of just doing it! The part of the shaft that goes into the exhaust housing will be adjusted a little toward the rear when making this adjustment. That way, when rotated into forwarded that shaft will be travelling farther vertically and forcing the gearcase farther into forward gear. Try it until your hands and fingers tell you what I am talking about. When you finish your adjustment the shift handle should be in the detent and the additional drag should be lightly felt with no forcing of the handle.

Pappy said:

Yes that is what I meant. Play with the adjustment while rotating the prop back and forth until you feel the additional drag induced by the clutchdog fully bottoming out into the forward gear dogs. Make an adjustment and then keep one hand on the shift lever while rotating the prop back and forth and lightly force the shift handle farther forward and you should feel a difference between fully bottomed and not. Unfortunately there is no better way to explain this other than the common sense feel/experience of just doing it! The part of the shaft that goes into the exhaust housing will be adjusted a little toward the rear when making this adjustment. That way, when rotated into forwarded that shaft will be travelling farther vertically and forcing the gearcase farther into forward gear. Try it until your hands and fingers tell you what I am talking about. When you finish your adjustment the shift handle should be in the detent and the additional drag should be lightly felt with no forcing of the handle.

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Well worded! thats what i meant also.....buy a service manual for your motor, it is worth every penny!