Johnson 25 hp "sneezing"

[bigkahuna333]

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. When you run it hard or wide open it seems to run fine. Once or twice it actual cut off when it sneezed. Each time it sneezes there is a puff of smoke out the exhaust (more than normal). I have fogged the carbs heavily with deep creep and there is no change. I am starting to become concerned that it may be due to ethanol effecting the carb somehow. I have noticed the hose primer ball no longer holds pressure due to the ethanol eating up the check valve.

I know there are some great mechanics on here who probable know exactly what is going on with such a "new" motor.

Thanks

[denny-o]

Replace the primer bulb, and anything rubber that feels suspiciously soft... Put in a new set of NGK plugs - gap them... Bump up the idle screw a tad... Put a shock treatment of Ringfree through it with 5 gallons of gas and Penzoil Synthetic OB Oil, just go out and run it around at various speeds and burn up the 5... If the motor is still sneezing at idle after that, you need to see an OB mechanic to check the fuel pump, the electrical, etc...

denny-o

[SCAngler]

do what Denny has listed but you may need to check the low speed jet in the carb. i know you said you used deep creep but many times it does not get the varnish out of the jet.

good luck

[bigkahuna333]

Is the low speed jet accessible without pulling the carb off? Is there any way to clean it without taking the carb off? How do you identify the low speed jet? I have removed carbs before and rebuilt them (simple 1 cyl strokes) but not sure how complicated this one is.

[arrivi]

well your problem is simple. Dirty carbs. You own a 2 stroke engines therefore oil goes thru your carb jets mixed with gas. When not in use oil start building up in them and usually you have to take them apart and clean them up throughly ( jets and vents, and everything). this should take care of the coughing.

good luck

[Rusty]

make sure it's not running too lean or rich. That could have an effect on the idle

[denny-o]

OK Big K, I didn't know you had any carb experience...

Actually, along with what I posted, I would have ordered a fuel pump and a carb rebuild kit and gone though it (them)... You can get lots of suggestions for cleaning carbs but I use MEK in a 2 quart Mason jar/jug because I keep it on hand for the engine projects we always have underway - boat/car/bike/plane (many hardwares will have jugs and the MEK)...

Let the carb and parts soak overnight... Blow it out with compressed air.. Reassemble with the new gaskets...

The Ringfree is also for cleaning the fingers and the rings so do that treatment along with the carb rebuild...

I am in the process of resurrecting three 1960's Chrysler 45 hp motors, so have heard lots of sneezing in the past few weeks and have been doing carb rebuilds like popcorn...

GL

denny-o

[bigkahuna333]

I am suprised I would need to rebuild the crabs in a motor that only has 10 or 15 hours on it? Not questioning any of the advice here but sounds extreme given the circumstances. Is it because it has varnished up somehow? This leads me to the question/debate of weather to leave fuel in the carb or to run it all out after use and during storage. Many years ago I was told to always run the fueloutof the motor and carb. A couple years a go a certified boat mechanic told me to not do that. He said it is better to leave fuel in the motor and give the ball a few squeezes every so often to keep it full. He said no air no varnish. What is the preferred method now ith ethanol fuels?

[denny-o]

Letting the carbs run dry means air in there which will dry wet surfaces turning them to varnish... I don't do it..

The hours on the carbs is meaningless... It is whether or not you have varnish narrowing the jet...

A carb sitting after having been soaked can have the gaskets dry up and get hard and start leaking air...

Most likely in your case is the carb... Next is fuel pump getting air bubbles... Next is intermittent spark... Last is vanes...

denny-o

[Eggsuckindog]

I am suprised I would need to rebuild the crabs in a motor that only has 10 or 15 hours on it? Not questioning any of the advice here but sounds extreme given the circumstances. Is it because it has varnished up somehow? This leads me to the question/debate of weather to leave fuel in the carb or to run it all out after use and during storage. Many years ago I was told to always run the fueloutof the motor and carb. A couple years a go a certified boat mechanic told me to not do that. He said it is better to leave fuel in the motor and give the ball a few squeezes every so often to keep it full. He said no air no varnish. What is the preferred method now ith ethanol fuels?

No need to any of that stuff - its lean at idle - look at the front of the carb up top front, there will a screw there - turn that out while its running. You'll hear the difference in the motor 1/2 turn should do it.

Its an air jet not a fuel jet, if need be turn it all the way in, counting the revelutions - then take it out but that will tell you where it was - run some soft copper wire or mono in if it needs but should only need richening a bit.

Stop in at a dealer or call and ask where it is on that motor but it shouldn't be hard to find just looking.