Spark plug fouling

[vettman]

2016 Yamaha 115 LB 4 stroke fouling out a plug or two every 150 hours or so which is about a year and a half a time. On a pontoon which I run at 3300 to 4300 rpm when out. Ethanol free gas used. Filters changed. Once I change out plugs runs fine until the next 150 hours or so. Is this normal. I shouldn't think so. Thanks

 

[robert graham]

A good bit of idle speed, low RPM running, older gas that's been sitting in your tank for a while could be possible reasons. Do you use any kind of fuel stabilizer like Stabil or Yamaha Ringfree or others?.....

 

[vettman]

No stabilizer as of yet. Do I need it with ethanol free gas. As stated I run 3300-4300 cruising around. Probably 3 hours each run 3 times a month. Just thought fouled plugs on a 4 stroke was unheard of. Runs great with the new plugs but then one decides to foul after the hours stated. I noticed that the newer LB runs smaller, 12 mm plugs compared to the older LA 14mm size. Do t no why smaller would be better. Guess they cant handle the heat.. PS. Just before I'm done with an outing I run it hard for a few minutes before docking. Thanks for your input

 

[robert graham]

If the gas is sitting in the tank for several weeks or months at a time, even if you're topping off the tank with fresh gas from time to time, your fuel may be getting old....I run Stabil or similar stabilizer all the time to keep gas fresh.....I run the 10% ethanol regular 87 octane....my motor is a 1999 model and never any problems.....and no fouled plugs....Just curious, but are your plugs fouling with gas or oil?....or can you tell.

 

[Sea Rider]

Check oil level in dipstick, probably too much. 4 stroke motor tend to make more oil that the amount previously added...

Happy Boating

 

[vettman]

The fouled plug is dry and black and not firing. No oil residue. Oil level is where it should be. Will try Yamaha ring free. Could it be s bad injector or dirty one. The new plug(s) last awhile then fail at about 100 hours or more. Seems if injector was bad it would do it all the time and right away. The F115B is new generation as of 2016 I think. Just wondering if any one has one that has the same problem. Sometimes new generations are developed because the old ones are too good and last too long. If you know what I mean. Thanks for all your inputs. Will just carry new plugs and a 5/8socket with me. Just like in the old days running 2 strokes.

 

[Sea Rider]

Is it possible to have all the inyectors cleaned and calibrated at an injector cleaning facility to rule out one is already faulty. If having that type of problem seems it's a injector or a Ignition Coil related that must be checked with a spark tester to determine if the spark is firing and check its intensity

Happy Boating

 

[schematic]

you may also be over-proped which causes rich mixture when being lugged. check maximum rpm vs recommended rpm.

 

[tblshur]

might want to check thermostat for stuck open condition