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2016 BF115 rough idle one minute smooth the next

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fishnmaine

Contributing Member
Ok my outboard probably has 50 hrs on it. Ran fine in June took it out today. Running rough and the comes out of it for a minute then rough again. That’s on idle or even quarter throttle. I have old fuel and new fuel mixed together. Thinking of draining tank. I noticed when I’m squeezing the prime ball, on my water separator I can see bubbles every time. Maybe that’s normal. maybe it’s always done that but never noticed, still have the original plugs also. Even though it has a little hours every fall all the filters are changed. This motor is pampered never abused.
So thinking of changing the plugs, getting a new prime ball and replace the fuel what do you guys think?
 
How big is your fuel tank? If your 8 year old outboard has 50 hours on it, I’m thinking you could easily have an old fuel issue, especially if you have been using ethanol fuel.

If you have a portable tank, I’d drain it and refill with fresh high test, as high as available and non ethanol if available. Add a whole can of sea foam to that fresh fuel tank and then run your outboard on the water, not on muffs or in a barrel, at 2500-5500rpm for say 30 minutes. Go around in circles if you are on a small lake. -:) . See if that cleans things out.
 
NSDON said:
How big is your fuel tank? If your 8 year old outboard has 50 hours on it, I’m thinking you could easily have an old fuel issue, especially if you have been using ethanol fuel.

If you have a portable tank, I’d drain it and refill with fresh high test, as high as available and non ethanol if available. Add a whole can of sea foam to that fresh fuel tank and then run your outboard on the water, not on muffs or in a barrel, at 2500-5500rpm for say 30 minutes. Go around in circles if you are on a small lake. -:) . See if that cleans things out
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Fuel tank is 30 gal. First 3 years I ran ethanol but always stabilized it. Last 4 years when it became available non-ethanol. The tank never gets emptied or run low when I hit 1/4 of a tank I throw in 5 gal. Never filled to the top. When stored it’s 3/4 of a tank. I’ve got a pump so all fuel will be taken out. And take it from there I guess I run the boat maybe 7 times a year if that.
 
Even though 50 hrs, I'd change plugs too. Can make a big difference. But I would drain tank 100%, fill up fresh fuel. If you had a jug full of pee, and emptied most of it out, then filled with water, you'd still have piss water.

Diluting old fuel doesn't make it better. It's still there.

Also check for possible air leaks if you have bubbles in water separator. I'd also try a new primer bulb and fuel line. Make sure fuel filters are tight, and use grease on rubber gaskets and o rings.
 
codycat said:
Even though 50 hrs, I'd change plugs too. Can make a big difference. But I would drain tank 100%, fill up fresh fuel. If you had a jug full of pee, and emptied most of it out, then filled with water, you'd still have piss water.

Diluting old fuel doesn't make it better. It's still there.

Also check for possible air leaks if you have bubbles in water separator. I'd also try a new primer bulb and fuel line. Make sure fuel filters are tight, and use grease on rubber gaskets and o rings.
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I noticed fuel line from primer bulb clamp wasn’t tightened. But line was in there really tight. I tightened it anyways but don’t think air would have gotten in. Takes allot of force to get line disconnected. Will be doing all of these things suggested. Stay tuned!! lol
 
Borrow a portable tank and try running it that way. You might be better off using 2 portable tanks all the time with the low number of hours annually? You can easily drain them at end of season and burn the fuel in a vehicle.
 
Would you guys run V-power NGK or Iridium NGK? Standard equipment on the motor is v-power. This is for a BF115, One plug seemed not to be firing from the looks of it. Hopefully a bad plug if not I would say coil
 
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