1991 Johnson 8hp - Lean Sneeze

Hi Guys,

My first post, and I am frustrated!

This outboard runs great except.... I cant get the idle right.

Carb has been disassembled and properly cleaned several times...

The engine will only idle well at 3 turns out... which seems really rich... and even at 3 - 3.5 turns out I can get it to sneeze by quickly revving it up from idle. It wont even idle at 1 1/2 turns out.

If it sneezes and stalls.. it is then hard to start.

The only thing I see is the gasket between the bowl and carb body seems to be leaking slightly, but this should not affect the mixture...

Any ideas...

Thanks in advance.

Re: 1991 Johnson 8hp - Lean Sneeze

Is this a new to you engine or have you had it awhile? If you've had it awhile did it just recently start doing this?

Re: 1991 Johnson 8hp - Lean Sneeze

This is my first season with it. So I guess new to me.

I have been trying to get this idle right since I bought it.

The main problem is when trolling.... it inevitably sneezes and stalls. No problems at high speed.

If I turn it off with the kill switch, it starts well warm or cold.

Ideas?

Thanks,

Re: 1991 Johnson 8hp - Lean Sneeze

Do you have the Johnson manual for that engine? There is quite the extensive linkage and carb set-up procedures that need to be followed. Do you have the idle stop screw adjusted properly? Throttle cam? For instance, the throttle roller should be lined up with the mark on the cam when the throttle is in the fully closed position. Although my manual for my '87 tells me to disregard the cam mark. It sounds though as your timing at idle might be off. I would reset all the linkage according to the manual.

Re: 1991 Johnson 8hp - Lean Sneeze

I do not believe the idle timing is adjustable on the 1991 model, but I think that you may be right regarding the linkage.

I still dont understand why I need to run the idle screw at 3 - 3 1/2 turns out.

I will try to fine tune the linkage using the manual.

Re: 1991 Johnson 8hp - Lean Sneeze

yes the idle timing is adjustable by undoing the throttle cable at the adjuster and advancing or retarding the timing plate and setting the stop on the right side under the flywheel. I think yours should be set at 8 or 9 ATDC with a timing light at 700-800 rpms.
Check the carb butterfly shaft for air leaks with wd40 or carb cleaner when it is idling. you might even have to open the idle needle to about 5 if you have leaks. I just found I need to set my idle needle about 5 1/4 turns out due to leaks at the carb shaft. I reset the idle timing and now have full throttle response. I need to get it on my sailboat for the real test though. By the way, your 91 8hp and my 87 6hp are the exact same engines except for the carb, and I believe you have a rev limiting CDI. You get the extra two horse only from increased rev limit due to the carb hi speed jet. The bore/stroke and displacement are the same on both engines.
Paul

Re: 1991 Johnson 8hp - Lean Sneeze

Thanks for the reply. I will check for leaks.

I read that the 91 did not have adjustable idle timing though. The manual I picked up indicates that it was only adjustable on the 1990 and before.

Re: 1991 Johnson 8hp - Lean Sneeze

"The only thing I see is the gasket between the bowl and carb body seems to be leaking slightly, but this should not affect the mixture..."
I would first fix this problem before going further. If you get everything right and have to remove the carb. after you have to link and sync it all aver again. Best of luck. Rick.

Re: 1991 Johnson 8hp - Lean Sneeze

Thanks Rick. I agree. I just ordered a carb kit.... Its driving me nuts... runs great and starts perfect.... I can even get it to idle well... until it sneezes!

Re: 1991 Johnson 8hp - Lean Sneeze

Did you ever resolve the "sneezing" issue?