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Shift Linkage adjustment? 1980 Johnson 15hp

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xltom

Contributing Member
I bought an 80 Johnson 15hp(J15RLCSD) recently that wasn't pumping water. I pulled the lower unit and replaced the impellor. After I was done I tested the motor at a local lake for about an hour and had no problems. Yesterday I was running the motor wide open when I heard a pop and then it started slipping out of gear. I had to limp back to the boat ramp. It took an hour and a half as any amount of throttle caused the motor to slip out of gear again.

I've done some reading which indicated that the problem is most likely the clutch dog and forward gear UNLESS the shift linkage is out of adjustment. Is there somewhere to adjust the linkage on these motors besides the obvious coupler that must be removed to drop the LU? There is no adjustability there other than the possibility that it is not seated properly. I'm just looking to rule everything else out before dismantling the gearbox. Thanks for any help... Tom
 
When you put the lower unit back on did you line up the notch in the shift rod with the hole for the bolt ( in the bracket ) --------------IT MUST BE LINED UP !
 
I'm pretty sure I did. I'll have to check when I open it up of course. By the way, there was a lot of floatin debris on the day she started slipping so I may have hit something. My gearbox is still holding oil.
 
Last edited:
racerone said:
Now you mention the debris !!----------------------Try another prop after you check the shift coupler.
Click to expand...

don't have another prop..... is there a way to check the one I've got? Is it designed to break on impact? I noticed the lack of shear pins on this motor.
 
racerone said:
It has a rubber " slip clutch " that may have failed.-----------------A close inspection may show damaged rubber.
Click to expand...

I just talked to the people at the repair shop where I buy parts. They said if it was the rubber slip clutch the motor wouldn't go into gear and slip/pop out repeatedly. They said the prop just wouldn't spin. I think this sounds fishy and I've recieved bad advice from them before. What do you think?
 
I have seen slipping hubs for some 40 years ---------------Perhaps a " google " on the subject will help explain this for you.
 
racerone said:
I have seen slipping hubs for some 40 years ---------------Perhaps a " google " on the subject will help explain this for you.
Click to expand...

OK, I did the search. I saw people saying that intermitant slipping was possible and some that said it wasn't. I saw one thread where the symptom WAS intermitant slipping and and the hub did turn out to be the problem. I hope this does turn out to be the problem because a new clutch dog and forward gear will be expensive. I found a method of checking for a spun hub in my search. I will just mark the prop, hub, and propshaft then run the motor. If the marks don't line up afterwards it's a spun prop.

Thanks for the help racerone!!
 
I marked everything and took the boat to a boat ramp. I put the rear end in and ran it wide open untill something slipped. I checked my marks and they still lined up. No spun prop. I dropped the LU and pulled the screw from the shift linkage being carefull to not let anything move. I looked though the vacant screw hole and it apeared to be lined up with the slot in the shifter rod. I think everything was correct there as well...which only leaves clutch dog and forward gear correct? I am draining the lube out of the gearbox now. If I am able to get the bearing housing out without a puller, I'll post the condition of the gears and CDog. Does any one know whether I need to pull out the drive shaft and shift rod first?
 
I just put the gearbox back together. The C-dog and F-gear look just fine. Doesn't look like they ever slipped at all. Hmmm... I'm thinking maybe testing the prop with the boat on the trailer didn't work... slipping might have been cavitation that time? Or maybe my linkage was mal-adjusted after all? The only other thing I can think of would be the yoke n lever.. but again the c-dog looked like it never slipped once...so.. I'll take it to a lake tomorrow for a full test... no new seals yet till I know I won't be tearing it open a bunch more.
 
UPDATE!!!! Loud pop today and the motor was slipping out of gear again. I brought tools to drop the LU luckily this time. I intentionally mis-aligned the shift linkage coupler to make the entire linkage longer, to push the clutch dog tighter against the forward gear. Had her up and running again in less than an hour. It now seems the shift linkage may be bent too much from people forcing it into forward gear... or the inside of the coupler is worn out... allowing it to slip. In any case the problem has been isolated.. thanks to everyone who helped out.
 
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