Johnson 50 Falling out of gear

[canemode]

Hi, I have a 1998 Johnson 50HP 2 stroke. Great motor by the way. On the weekend I was off fishing heading up the river when the revs suddenly increased dramatically and I lost all drive. I put it back in neatral and tried forward again and it was ok at first but under load it did it again, so I tried reverse and same thing under high revs or load it seems to be dropping out of gear. I took the cowling off and checked the linkages, but all fine and doing what they should, so I watched them while driving and they stayed where they should yet it still dropped out of gear. I checked the controls to see if all ok in there, but everything looks to be fine and no wear etc. Something is wrong inside which is the next step having idled it back home in gear fine. Can anyone give an idea of the likely cause before I start dismantling the leg please. Is there a clutch in the leg, it seems identical to a slipping clutch in a motor cross bike to me.

Any help or direction is aporeciated.

 

[HighTrim]

Re: Johnson 50 Falling out of gear

Is it jumping out of gear, or simply over revving?

Jumping out of gear would lead me to believe that your clutch dog is worn. They have precisely machined edges, that mate to the forward and reverse gear. When these edges become worn, and the RPMS increase, the dog and gear are forced apart, giving the sensation that you hit a log. This is usually caused by improper shifting by the operator. You need to snap the unit into gear in a sure, quick movement. Slowly easing it into gear causes the edges to bang against one another, rounding them.

If it is over revving, yet not moving, I would test the prop hub, to be sure that it is not spun. Draw a line across the hub and prop, then run it until you her it 'rev'. Then observe, if the lines are no longer lined up, she is spun and will need to be rebuilt.

 

[tashasdaddy]

Re: Johnson 50 Falling out of gear

sure sounds like a spun prop. if it were gears you would hear grinding.

 

[HighTrim]

Re: Johnson 50 Falling out of gear

Welcome back TD. Hope your trip to the Keys was a good one!

(sorry to get off track)

 

[canemode]

Re: Johnson 50 Falling out of gear

Thanks for the quick replies fella's, I will check for spun prop this weekend and update you. Hopefully this is the prob rather than the clutch or something else, this has been a great motor so it would be good if it was not internal. Watch this space next week

 

[canemode]

Re: Johnson 50 Falling out of gear

I took the prop off and there was melted rubber around it and the hub looked destroyed and was very soft, so pretty sure the prop was spun, so I put my neighbours on and it went fine for about 20 minutes and then same thing. I took that prop off and looked at it to find the similar symptoms to my prop, so now I owe him a prop. It was fine when I put it on. Now the question is can anything be causing this or is it a coincidence that his was about to go as well. Something must be causing this.

 

[tashasdaddy]

Re: Johnson 50 Falling out of gear

have them both rebuilt. they will be like new. the only thing i can think of is that the exhaust, is some how melting the rubber. i really suggest you start a thread in the prop forum. and give all the history.
http://forums.iboats.com/forumdisplay.php?s=&daysprune=&f=35