extremely high idle suddenly

[Jmurray65]

I was coming off the lake yesterday and all of a sudden, when i throttled down my idle stayed at 4000rpm. I had to go to the motor and loosen my idle adjustment screw... can that screw just self adjust to a high idle?? seemed fine after making that adjustment. also noticed the throttle was tight when going to neutral, once adjusted.. felt normal again.
1993 Johnson 70HP

 

[alldodge]

I would look first at the throttle control, something could be binding or not moving as it should

 

[jimmbo]

When the Idle Speed is Adjusted, the Length of the Throttle Cable will also need to be adjusted to provide a bit of Preload. Too much Preload, and Shifting in and out of Gear can be tough, whilst not enough, can result in inconsistent Idle Speeds. However 4000rpm would be a bit high for that. As alldodge suggested, a bit more inspection of the Throttle Linkages under the Cowl need checking.
By Chance, you hadn't been in there adjusting Screws, other than the correct One for setting the Idle Speed. BTW, the Carbs should be fully closed for most of the Throttle Arm's movement

 

[saltchuckmatt]

How long was it at 4000 RPM's? Not long I hope....in neutral?