Johnson 15 jumps out of gear

[bigfatdaddy]

Mid eighties sea horse johnson 15 jumps out of gear about 3/4 throttle. I've replaced clutch and clutch dog. dealer wants me to spend $200 on used bottom end. Can I fix it for less and what is wrong?

 

[Xcusme]

Re: Johnson 15 jumps out of gear

Welcome to iboats!

Possibilities:

Worn replacement forward gear and dog or improperly installed shift rod coupler come to mind.

 

[bigfatdaddy]

Re: Johnson 15 jumps out of gear

Thanks. I'm betting the forward gear and dog are installed correctly. I took it to a reputable dealer for repair. They've had it five times. I gave up and took it home. The problem doesn't occur until after about ten minutes of run time. It does that every time.

 

[F_R]

Re: Johnson 15 jumps out of gear

The ten minutes of run time is interesting. One would expect it to do it the first time you opened the throttle. Are we missing something? Is it actually coming out of gear or just slipping or what?

 

[bigfatdaddy]

Re: Johnson 15 jumps out of gear

It slips out of gear and the engine revs up. As the motor idles down, sometimes it will jump back in gear and sometimes I have to go to neutral and then back forward. It is curious about the ten minutes warm up time. I just don't know.

 

[ezeke]

Re: Johnson 15 jumps out of gear

Have you checked to see if you have a spun propeller?

 

[F_R]

Re: Johnson 15 jumps out of gear

Broken shear pin? Actually, I suspect something is still amiss in the lower unit and/or the shift linkage is worn loose and sloppy. Probably the loose and sloppy.

 

[ezeke]

Re: Johnson 15 jumps out of gear

Sorry for the question and lack of explanation. The 1980's 15HP motors were through-hub exhaust with the constant heat on the hub of the propeller that is normal to this type of exhaust.

There is a rubber grommet between the inner and outer portion of the propeller hub which over time can degrade to the point where it will slip. Fatigue and the heat of running may be causing the prop to slip on the grommet.

Lots of slipping props will regain their grip temporarily when allowed to cool a bit and at lower speeds.

Mark the hub across the inner and outer surface so that after experiencing the problem you can see if they are still alligned. There is no shear pin.

 

[bigfatdaddy]

Re: Johnson 15 jumps out of gear

Thanks for all the help. I will check linkage first. I think that may be part of the problem.

 

[tommays]

Re: Johnson 15 jumps out of gear

Anything i have seen slip OUT of gear would over REV really fast AND be very violent when it went back into gear ?



Tommays

 

[bigfatdaddy]

Re: Johnson 15 jumps out of gear

That's exactly what it does. Sometimes it slams back into gear before I can get it idled back down. Other times it idles back down and I have to go back to neutral before it'll go back into gear.