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BobT

Throttle hanging up

5 posts in this topic

1998 Johnson 90hp, 4-cylinder, 2-stroke, oil injected.

The engine has been a great performer but recently it has been having trouble idling down. I did a little checking and I noticed that the throttle linkage appears to be hanging up and I have determined which one it is. There are two throttle shafts connected in tandem. I couldn't see anything obvious that would be causing this but I can manually push the linkage down to the idle position. It felt sticky or dirty or something so I lubricated the shaft at all pivot points with WD-40. At first I thought it helped a little but yesterday the problem returned. I checked the screws that hold the throttle plates onto the shaft to make sure they are all tight.

Are there any seals on the throttle shaft that could be needing attention? The only other thing I can think of is that maybe a throttle return spring broke?

Any suggestions?

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I would start with disconnecting the throttle cable (try and remove the circlip first and see if you can get it to pop off... if not, disconnect the holder by the finger screws and it should pop off) and make sure that it'll return to idle on it's own first... to isolate control box / throttle cable vs linkage.

marine_man

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I've disconnected all the linkage to the throttles and have narrowed it down to the right one as you look at it from the intake. The cable connects to the left one and then linkage interlocks the right one to the left one. I guess you probably already know that, sorry.

If I manually open the throttle and then slowly let is ease itself back down to the idle position, I can feel a slight resistance just before the throttle gets all the way down to the idle position. I can then manually turn it the way down if I overcome that resistance. If I open the throttle and then let it return on its own spring tension, it snaps all the way back to idle position.

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I believe I found the problem. Between the upper and lower carburetor I noticed a split brass clamp on the throttle shaft that was rubbing on the top side. I just can't explain why after all these years it suddenly began to rub. All I did was loosen the socket head screw holding it in place and slid it down the shaft just ever so slightly and re-tightened the screw so the clamp had enough clearance. It was a little tricky getting in there. Fortunately I had a long enough screw driver to reach. Throttles seem to work nice and smooth now.

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