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charlo slim

2 stroke outboard problem - any suggestions?

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charlo slim

My '05 25 hp Johnson 2 stroke outboard has been near perfect since new.  Then the other day I was zipping along at about 80 % throttle when it gave out with a major cough / sputter and began running very rough at anything much above idle speed. It starts fine and seems to run fine at low speed, but goes in to the cough / sputter mode whenever I open up the throttle.  I have checked for water in the fuel, checked fuel filter, and replaced spark plugs -- no dice there. 😟  I know, I know -- take it to the shop, dummy!  Problem is that I would likely be out of business for several weeks under that plan, just as the annual lake whitefish bite on Flathead Lake takes off.  

 

Any experience / thoughts on what may be going on, or any ideas on potential solutions that a yokel with only minimal mechanical aptitude (that be me) might pursue?  

 

Thanks very much.

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salmontogue

High speed carburetor jet may be clogged.  Internal fuel filter (located near the carburetor) is clogged.  Carburetor float is hanging up and/or the float valve is clogged.  These are relatively simple outboards and the problem you describe can be associated with unwanted goop in the fuel delivery system.  You might want to spray some carburetor cleaner in the carburetor throat while running to see if there is a change.  This may be enough but this solution is usually only temporary.  Carburetor jets are small and subject to clogging particularly in a mixed fuel environment.

 

A weak coil will sometimes break down at increased speeds.

 

Happy to discuss this by phone if you wish.

 

Perk

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Chief Paduke

Start with simple things. If you run gas with ethanol, replace the fuel lines, starting at the tank. 

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erik meade

I agree with the others.  Especially the high speed jet. That is where I would start. Those holes are tiny. Easy to clog up. 

 

Also if I got it running I would throw some Sea Foam in it just because I like putting Sea Foam in things. 

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aje4

I agree with the high speed jets....easy to open up and clean out with a pin head....

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Jim Vander

Id bet carbs as well order a rebuild kit, its pretty simple if you take your time.

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Virgil Kane

My 65 Mercury 20 HP did the same thing ( yeah, it's old but runs like a champ).  I replaced fuel line both inside the engine and new primer bulb and hose from the tank , rebuilt the carb, changed spark plugs, you name it and I did it including making sure the gas pick-up filter in the tank was clean .  It would run at idle but when given any throttle it would sputter and had no power unless I was constantly squeezing the primer bulb on the fuel line.  Turned out that the cork for the fuel tank gas gauge deteriorated and I had little pieces of cork in the bottom of the tank.  At idle there was enough gas but when given any throttle the suction  would draw more loose pieces of cork up against the filter in the tank filter and starve the engine of gas.  Once I cleaned the tank the engine has been running like it's brand new.  YMMV

 

Virgil 

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rolawson

Start with the fuel line. I had one do the same thing and it was caused by a crack in the fuel line. 

 

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Remo

Carlo, I have an '88 Evinrude 25hp that did the same thing this spring. The shop just cleaned the fuel filter on the carburetor and it seems to run fine at full throttle. I also put in the proper Champion plugs gapped at .30.

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ccavacini

If old gas (even if you used Stabil), that could be the problem.

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Peent

Run some sea foam through a tank.  Fixed a jet ski last weekend that had the same issue. 

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Mike da Carpenter

I too am a carb cleaner and Sea Foam kinda guy.  If at all possible run NON ethanol gas in an outboard motor.  As mentioned above, if the gas lines are old, they are quite possibly deteriorated on the inside (even if the outside looks awesome).

 

A couple months ago, My wife and I bought our boys a 14’6” Starcraft with a 15 hp Honda 4 stroke.  The motor was running like crap, and couldn’t hold idle.  The price reflected the “messed up motor”.  Before buying the setup, I offered to clean the guys carburetor and asked what type of gas he was running and if he ever tried sea foam in the tank.  He said “non of that snake oil will work, probably needs a whole new motor”.  I honestly tried to help the guy out, but my daddy didn’t raise a fool.  We gladly paid the man his asking price and drove down the road with the boat, motor and trailer in tow.  Stopped at the auto parts store once we got close to home for a can of carb cleaner and a couple cans of Sea Foam then the gas station to get non ethanol gas put the boat in the water.  Once I got it started, I cleaned the carb and poured a bottle of sea foam in the 3 gallon tank.  It took FOREVER to burn through those 3 gallons at full throttle (those Honda’s sip fuel).  Let it sit overnight after refueling and putting 1/2 a can of sea foam in the new tank.  The boys take it out every weekend, and I don’t have to worry if it is going to start for them and as long as they check their watch (phone) they will be at the dock when I show up to pull it out...that is if I’m not with them enjoying a day on the water with them,

 

It’s worth the money to give it a try.  I was skeptical my first time, but the stuff works, at least for the issues I have had in the past.

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WI Outdoor Nut

Like others have said, this is a fuel related issue - as you are not getting enough fuel once you open it up.  I would start with the easy stuff, already mentioned.  New fuel line, bulb and fresh, 100% gas.  If that does not work, then take apart the carb and guessing you have an issue with your main jet. 

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Flush

It is most likely a fuel related issue, but most of the time jets get clogged it's from when they are sitting around, not when they are cruising along at 80% throttle and suddenly they clog. 

This can happen, but if it does it's highly unlikely that running sea foam (or the like) is going to unclog it. You will need to take the carb apart and clean the jets as a piece of debris got sucked into the jet while the engine was running. The good news is the main jet (which is the one that would effect higher-rpm performance) is usually the easiest to get to and to clean.

 

I also like SeaFoam and it's easy enough to run some through it and you might get lucky and it cures your problem, but given how the problem popped up while in use I personally would not be optimistic. 

 

Like everyone else said, I would start with fuel delivery. Did you try squeezing the bulb while running at open throttle and did that make any difference? Check the lines and make sure plenty of fuel is making to the carb and then clean the carb. 

 

With all that said, although less likely it is also possible it's spark (coil) and/or timing advancement related. 

 

 Good luck and let us know what you find

 

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topdog1961

Check any grounds of the electrical system to the block. First unhook the battery, then take all ground connections loose one at a time, hit them and the block with a little fine sandpaper, reattach. It won’t take long and it won’t run right if a ground isn’t making good contact. 

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