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Forward to reverse

J

jjohn

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I have a 15 horse johnson.one

I have a 15 horse johnson.one day on the river the motor jumped from forward to reverse. I put into forward and a few minutes later it did it again. the motor seemed to run ok other than the shifting problem. by the time I was almost back to load the boat it quit running. I pulled the flywheel off and the key has sheared. could this be caused from going into reverse while cruising? or could it be going into reverse due to timing issue and backfire due to sheared key? about 3 weeks before I lost a prop on a tree in the river. but it ran fine for several outings after that until the shifting issue.could the shifting issue have just finished off a half way sheared key ? your help is appreciated
 
"IMHO I don't think that a

"IMHO I don't think that an OB that is underway can begin running backwards without stopping first, or at least a loud back-fire, etc. I'm guessing lower unit problem. If the lower unit seizes, I imagine that could have sheared the key."
 
"I dont beleive the engine ran

"I dont beleive the engine ran backwards. the shift selector was in the reverse position. when in the river I run with the tilt lock released incase I hit a tree, log, rock, or any of the many hazards. while underway the motor flew up out of the water into the tilt position, which is what happens when you hit something. I could find no evidence of hitting something. when I lowered it back down I noticed it was in the reverse position. I moved it back to forward and continued underway. a few minutes later the same thing happened so I headed back to the launch. When almost to the launch it was running worse and died. this is when I found the key. evidence shows IMHO the key was improperly installed and slid down allowing the flywheel to spin ( slight marring on lower section of flywheel from key about 90 degrees ) the nut was tight. I can find no evidence of lower unit seizing. I cant figure out how it finds it way into reverse while running. I have heard of lower unit probs where it jumps into neutral but not all the way to reverse. I have only used this engine 4 times. the first 3 no probs. can a backfire due to timing cause this jump from F to R or am I just lucky with multiple probs. can one be the result of the other?? the key wasnt completely sheared but bent as it looks like it slid down. it was sitting under the flywheel in one piece. there was some skag damage when I bought this motor. evidence to a previous prob? could that have caused lower end damage leading to shifting prob and maybe they installed the key improperly?? sorry for so many questions but I do thank you"
 
I went to that link and could

I went to that link and could find nothing on an engine jumping from forward to reverse I know it wont run due to sheared key. I am looking for cause and effect. the thing I cant explain is the shifting to reverse on its own. thanks for the link it will be very helpful.
 
I can't imagine any scenar

I can't imagine any scenario where an engine would jump from forward to reverse. Sorry! Hope someone else has some ideas.
 
well if no one has any ideas I

well if no one has any ideas I guess I will grab a key tomorrow and see how much further damage I can do. I cant explain it either. I know it is possible for a two stroke to run backwards if timing is far enough off but to actually shift itself thats beyond me. well cross your fingers and wish me luck. I will get back with the results.
 
"Scratch my other 1/2 @#%&

"Scratch my other 1/2 @#%& advice. If when it starts going backwards, you re-shift the lever to forward, and then you are going forward, then the engine definately is not running backwards. I can only imagine that you have some type of serious issue with the detent in the lower unit. You may want to check the magnet on the bottom drain screw for shrapnel."
 
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