Yamaha 4-Stroke Gasoline from Air Intake ??

[Dan366]

My 2000 115 Yamaha 4-Stroke has only 200 hours on it, and has worked perfectly until today.

It started rough, but at times seemed to run fine. At other times it ran rough or the rpm's dropped off. It seemed like bad gas, but the water separator was clean. There was one period when at ran good for 5 minutes at full throttle, so it doesn't seem that there would be a filter problem.

When I got home, I gave it a good visual, checked the gas again, checked the main fuel filter, and looked at the plugs. The only thing I found was that the plugs were all black instead of gray--indicating that it was running way too rich.

I started it and watched it run at idle, when I saw gasoline running from the air intake baffel.

I decided that I would get some input from the forum before I start taking things apart.

Any suggestions would be appreciated. Thanks in advance.

Dan (Florida)

 

[AGENT 37]

Re: Yamaha 4-Stroke Gasoline from Air Intake ??

If that were happening with mine, I have a 99 F100, I'd figure that the float needle was sticking and would probably pull the carbs off, clean them out and check the gaskets for any leaks. Fuel leaking out into the motor is a fire hazard and I wouldn't run it until it's fixed. Try pressurizing the primer bulb and watch on the inside and outside of the carbs with the air box removed to see where the leak is as a starting point.

 

[rodbolt]

Re: Yamaha 4-Stroke Gasoline from Air Intake ??

the F115 is an EFI motor. no carbs.
it does have a needle and seat in the vapor seperator.
if the needle is worn or has debris in it the tank overflows and gets vented to the air box area.
it may be time for VST maint. should be done yearly anyway.
drawback i it requires intake manifold removal to access the vpor seperator.
takes 1 1/2 hours or so.

 

[AGENT 37]

Re: Yamaha 4-Stroke Gasoline from Air Intake ??

I didn't realize that the 99 F115 was EFI, I guess that I never really checked assuming that 75 to 115 were all the same. My mistake.

 

[nolanmci]

Re: Yamaha 4-Stroke Gasoline from Air Intake ??

hi,I have 60f and having similar problems it idles fine then i jump on it,then after a while it started to bogg down like that.so im tryin to find a solution
also.maybe factory problems?