Gasoline in Oil 2001 F115

[Little Fish]

Hello all...wondering if you might give me some ideas on how to fix a problem with my Yamaha 4-stroke 115.

The problem started when I noticed my engine bogging down when trying to run at higher RPMS. I figured it was some sort of fuel system problem since they guy I bought from didn't use the engine that much. At any rate I ran several bottles of Techron through the system and that didn't help much. In fact it seemed to make the problem worse freeing up lots of crud in the system. I ended up taking the high pressure tank apart and cleaning all the varnish out then testing the engine. After the test I checked the oil level and it was overflowing. This happend after only running the engine for 20 minutes or so. I drained the oil and it was obvious it was very diluted with gas. Refilled it and tried again. I can now get 4400 rpms (should be able to get 5500), but after running the engine the oil tank was filled with gas once again (only ran it 30 minutes). I have no idea what the problem may be, but I'm running out of time to get it fixed before a week long boating trip. Any ideas what may be going on?

Thanks for your help.
LF

 

[Pas Bon]

Re: Gasoline in Oil 2001 F115

Don't feel alone. and don't expect any good answers. This seems to be a chronic Yamah problem and I have gotten multiple answers from bad T-Stats to rings not seating to needing to use ring free etc etc. Bottom Line is yamaha has a serious problem that they need to address. I have a 2002 115 with 155 hrs and I have not had a serious problem yet.

Also one of the first things you will hear is that the motor is over propped.

Do a search on "making oil" and or "oil in the gas " there are entire threads dedicated to it.

http://forums.iboats.com/showthread.php?t=144636

Good Luck

 

[Little Fish]

Re: Gasoline in Oil 2001 F115

Dang. That doesn't sound good. I will check it out. Thanks for the link.

 

[Little Fish]

Re: Gasoline in Oil 2001 F115

Just a quick recap for those who are interested. The bogging down of the engine was most likely caused by varnish build up in the fuel system and got worse when I used techron to try and clean it out. The solution was to pull and clean the injectors plus pull and clean out the high pressure/VST tank. Also checked the float and shut off valve in the top of the tank while it was apart. Lots of junk in the tank plus injectors were clogged.

The gas in the oil problem was most likely caused by a failed diaphram in the fuel pump located on the back of the engine. Due to the volume of gas in the oil and the short time for it to build up this seems like the most logical conclusion. I did however change the thermostat for good measure. I'm not certain, but it seems likely that the diaphram failed after being in contact with the techron in the system. Not that techron is that potent, but the diaphram was old and tired (7 years) and ready to give up the ghost.

Thanks for the help everyone.

 

[BaileysBoat]

Re: Gasoline in Oil 2001 F115

How many hours on that F115?

Were you running with a 10 micron water separating fuel filter?

The diaphragm filter would account for the oil dilution but what about the clogged injectors?

 

[BaileysBoat]

Re: Gasoline in Oil 2001 F115

Sorry, meant to say diaphragm "failure"

 

[Little Fish]

Re: Gasoline in Oil 2001 F115

300 hours on the engine. No on the 10 micron filter....until just recently. Apparently back when the motor was made/installed Yamaha didn't spec a 10 micron filter?

Another contributor to the clogged injectors was the fact that this engine had very few hours on it when I bought and had sat for awhile. It was obvious when I cleaned things out as you could see flakes of varnish at the bottom of the high pressure/VST tank.

I think the clogged injectors was a combination of things....not using a 10 micron filter for 5 years, not being run very much over that 5 year period, running techron through the system which loosened everything up, but didn't dissolve the varnish all the way.