Johnson 25 hp "sneezing"

[Eggsuckindog]

well ???

[mike young]

I never owned a Johnson or Evinrude that didn't cough or spit and sputter at idle. I thought it was normal.

[iMacattack]

Couple notes on small motors and ethanol.

First corn belongs on the cob not our petroleum!

Second anything remotely resembling ethanol belongs over ice and served by the shot.

Lastly ethanol is one wicked cleaner/solvent. (old racing fuel cells would melt when ethanol was introduced)

With that out of the way. If you have confirmed you have ethanol in your fuel and it's old and untreated... dispose of it properly. I had a problem with ethanol on a 2008 Yamaha 4 stroke F40 carbed outboard. In less than 30 hours of use on a BRAN NEW motor on a BRAND NEW skiff. All three carbs were replaced at least once.

Ethanol basically crystallized on the idle jets. Much like a grain of sand in an oyster the ethanol pearl would grow to the point that the motor would refuse to start. Nothing like trying to start a 4 stroke 6am in the summer in Flamingo while being drained of your blood by all the skeeters! Yamaha did help out and covered the replacements under warranty. I have since spoken to a few reps at Yamaha and out in the field. There are a few other solutions that include a specialized ultrasonic parts cleaner to soaks in MEK overnight. (as mentioned above)

The issue is that you might solve the problem for the short term but it will rear it's ugly head again unless you treat the source of the problem, ethanol. Every manufacture I have talked to while conducting a recent Four Stroke Shootout on my site all chanted the same tune. Treat your ethanol and use a 10 micron fuel filter, no exceptions! There are several options out there. Some are a bit OVER stating what they can do IMHO, but since we started treating the fuel, NEVER leave the tank less than full and run a religious regiment of checking and replacing our 10 micron filter, the problem has not returned. Coincidence? Not likely. I can tell you that many mechanics are just as stumped as we are with regards to ethanol. The manufactures are working hard to get everyone up to speed, but in the end we have to take the due diligence to research on our own and learn from our shared experiences.

Cheers

Capt. Jan

[thill]

I had the same problem. Find the low speed jet and close it firmly, counting the number of turns. Then back it off to where it was, and go 1/8-1/4 turn more open.

If this doesn't solve the problem, the carbs probably need to be cleaned. In my case, this cured my problem perfectly, and I didn't have to do anything more. Mine ran great for a year or two later, until I sold that boat. And the guy I sold it to still raves at how flawlessly it runs.

Give that a shot before you go whole-hog on the carb.

-TH

Edited August 5, 2009 by thill

[wilde1j]

"Sneezing" is a clear sign of running too lean. If you don't have a low speed mixture adjustment, a carb rebuild/cleaning is needed. Remove plastic parts, soak overnight in a suitable carb cleaner, blow dry after making sure all orifices are clear, etc.

[seahorse]

I have a 2003 Johnson 25 hp 2 stroke on a 16' carolina skiff. I bought the boat this winter and it had approx 10 - 15 hours on it. Ever since I bought it, the motor seems to "cough or sneeze" when idleing or running under light load at lower rpms.

Sneezing is from running lean but do not overlook engine temperature. The engine is designed to idle at around 140° so use an infrared temp gun to check the cylinderhead temperature and to make sure the thermostat is operational.

Also carbon stuck rings affect the idle and a can or two of Evinrude Engine Tuner run through it and allowed to soak overnight helps in a lot of cases.

Make sure the carb synchronization and linkage is adjusted correctly and that the throttle plate is completely closed at idle.

The carb of course has to be adjusted correctly, clean and no varnish or buildup in any of the passageways or jets. Gaskets and seals have to be in good shape also.