Johnson 15hp kicks at speed...any ideas? (Video)

[galveston]

I have a late 70's Johnson 15 outboard that "kicks" at speed/full throttle. This happens consistently and repetitively. If I back off the throttle just a touch, it ceases and the engine runs like a top.

I have been told it could be a clutch dog, prop ventilation/cavitation, spun prop, motor running lean, shifter link needs adjustment, etc.

You can hear it happening in this video from 00:19 to 00:30.

http://www.youtube.com/watch?v=b-2e3DW7g6Q

Are there anything tests I can do to verify the problem? When I spin the flywheel/prop by hand I can definately feel the gears catch and it feels solid. I have never had it slip out of gear. Anyways, I really like this motor and would like to fix this problem.

 

[catfishordie]

Re: Johnson 15hp kicks at speed...any ideas? (Video)

hi speed needle out of adjustment?

 

[dew2]

Re: Johnson 15hp kicks at speed...any ideas? (Video)

What do you mean by KICK,It seems it bogs down toward the end of the vid.unless thats you lettin off the throttle?

 

[galveston]

Re: Johnson 15hp kicks at speed...any ideas? (Video)

What do you mean by KICK,It seems it bogs down toward the end of the vid.unless thats you lettin off the throttle?

I got off the throttle.

By kick I mean the outboard jumps as if it is hitting something in the water. This happens repeatedly and it is not random. It does it consistently every time at full speed.

 

[SparkieBoat]

Re: Johnson 15hp kicks at speed...any ideas? (Video)

check sparks, compression and fuel..sounds fuel related to me..clogged carb maybe bad fuel line...also check your reeds

 

[Faztbullet]

Re: Johnson 15hp kicks at speed...any ideas? (Video)

By kick I mean the outboard jumps as if it is hitting something in the water. This happens repeatedly and it is not random. It does it consistently every time at full speed.

That usually a lower unit/adjustment problem. Has it always done this or have you serviced anything and this just started doing this?

 

[galveston]

Re: Johnson 15hp kicks at speed...any ideas? (Video)

it has always done this since we bought it.

 

[boobie]

Re: Johnson 15hp kicks at speed...any ideas? (Video)

Sounds like a fwd gear and clutch dog.

 

[galveston]

Re: Johnson 15hp kicks at speed...any ideas? (Video)

thats what i keep hearing the most.

 

[Faztbullet]

Re: Johnson 15hp kicks at speed...any ideas? (Video)

Yep.... dog and gear get my vote. Find a good machine shop and have them recut as cheaper than gear and dog.

 

[galveston]

Re: Johnson 15hp kicks at speed...any ideas? (Video)

so should i just buy a used gearcase or should i get a mechanic to fix it?

 

[jasper60103]

Re: Johnson 15hp kicks at speed...any ideas? (Video)

I tell yah, if it popped out of gear I certainly didn't hear it.
My 25 did that once and it was a loud bang, and it scared the crap out of me.

 

[kbait]

Re: Johnson 15hp kicks at speed...any ideas? (Video)

Didn't sound like clutch bang to me either. Perhaps when the stator plate is advanced fully (full throttle), one plug wire gets close enough to a ground to arc out intermittently?? Check the plug wires when motor is off and motor is in forward and throttle fully advanced. May be a barely noticeable pin hole in one plug wire. It's also possible for the cylinder the fuel pump draws it's pulse from is getting too much fuel (leaky fuel pump diaphram). That would only affect one cylinder. Those fuel pumps are pretty universal, so perhaps you could borrow one for a test? Also, be sure all the ground wires are properly tightened down.. especially the ones from each coil to their mounting bolt. Good luck! Oh, and if it's a '74-'76, it has points under the flywheel (newer ones have a CD box). Dirty points could cause this, as could a stator plate w/lateral play, as that changes the point gap. If it's '77 or newer, that's not the issue.

 

[galveston]

Re: Johnson 15hp kicks at speed...any ideas? (Video)

Here is a great comparison. I have my doubts that it is slipping in and out of gear. I would think it would be more violent and that the lower unit would shred itself in no time.

Here is a nearly identical motor. Listen to it. Sounds smooth.
http://www.youtube.com/watch?v=VPUO1KEju-U&feature=related

Now my motor. Sounds, runs great at 90% throttle but soon as you go all out it starts "wahwahwahwahwah" and the motor kicks in sync with these oscillations.
http://www.youtube.com/watch?v=b-2e3DW7g6Q&feature=related

Still stumped.

 

[jasper60103]

Re: Johnson 15hp kicks at speed...any ideas? (Video)

Ohhhh! I can hear the "wahwahwahwahwah". At least we can eliminate the clutch dog. I'm not sure what it is though.
Can you post your model number, that way we can nail down the year?

 

[galveston]

Re: Johnson 15hp kicks at speed...any ideas? (Video)

Ohhhh! I can hear the "wahwahwahwahwah". At least we can eliminate the clutch dog. I'm not sure what it is though.
Can you post your model number, that way we can nail down the year?

Sure will, I can find the manual tomorrow.

 

[jasper60103]

Re: Johnson 15hp kicks at speed...any ideas? (Video)

Sure will, I can find the manual tomorrow.

It should be a tag on the transom clamp with model and serial number.

 

[jrs_diesel]

Re: Johnson 15hp kicks at speed...any ideas? (Video)

I agree, does not sound like the clutch dog at all. Almost sounds like its hitting a rev limiter, even though these engines don't have them. Very strange.

 

[bktheking]

Re: Johnson 15hp kicks at speed...any ideas? (Video)

Is it a CDI motor, no points? If so , post the part number on the powerpack.

 

[SparkieBoat]

Re: Johnson 15hp kicks at speed...any ideas? (Video)

I still think post number 5 is a good place to start..that is not a clutch dog slipping.