Excess gas in oil of 2000 F115

[<Jim>]

I ***** quite a bit and after about ten hours I will show an excessive amount of oil in the crankcase. Lab test show the gas to be 5%, which they say will ruin the engine. I agree since I am on my third power head. I have had the thermostat replaced but the engine still runs too cold. Even when I dont *****, the engine oil reeks of gas after a few hours. Yamaha has given up.

[<boats.net>]

Yamaha did make some changes in the ECU for that problem. you might get your dealer to check with Yamaha to see if you have the latest version ECU,thermostats and spark plugs.

[<Greengilz>]

I've got 2 motors like that just out of warranty. One is in bits and needs a complete rebuild. Possible causes:
-injectors not shutting off properly (dirt)and over fueling or dripping. I belive the standard Yamie filter is 35 micron and all the injector experts I talk to say it should be 4 or 5 micron.
- Leaky needle valve in the tank between the injector pump and injectors - leaks to inlet manifold, cylinders then crankcase
- running too cold - computer thinks engine is in startup/warm up - over fueling

Search the net and you will other examples of similar problems (iboat).

We all need to get together to get something done about this: greenhough.k@xtra.co.nz

[<Bob T>]

I just stumbled on to this thread since I have a 2000 T-50 that is getting gas in the oil. It is carburated, not injected and I have not had an oil analysis performed. However, I can see the oil is thin and smells like gas so I know something is obviously not right. The engine has about 125 hours on it.

Any suggestions of simple things I can perform myself or should I just take it to a dealer and hope for the best?

Thanks for any and all feedback.

[<ScottB>]

Any news on this? I just bought a boat with the same motor and once I got it home I noticed the oil is thin and smells of gas. I'm not sure what to do. Now I'm afraid I bought a bad motor. Any help would be appreciated.
Thanks, Scott

[<forsailbyowner>]

anybody check to see if this is a crankcase evacuation problem? There should be a steady flow of air to evacuate blowby and gas fumes that make it past the rings. If it is a problem with an overrich fuel mixture is should be evident in spark plug color. If the plugs are tan this is where i would look.

[<gary N>]

I think you have a fuel pump diaphram crack or pin hole. I believe many of the yamaha's have this problem and it will pump gas into the oil.

I don't think Yamaha is really stepping up to the plate on this - as a defective fuel pump is a serious defect and it may be the material they use on this mechanically driven diaphram is not able to withstand the new gas we all use.

No way this should be happening on engins this new . My 9.9 has never run well since new.

Gary N.

[<Dave>]

I have a 2003 F225 that has gas in the oil, I have changed the oil three times and have only 62 hrs on the engineer. I have asked every Yamaha dealer I could contact about this, they keep telling me they never hear of it. Should I trade this in before i get into real trouble?

[<gary n>]

Dave

Make Yamaha face up to it. They claim to be the best and have customer service. Have them remove and inspect the fuel pump. Then demand they tear downa and inspect your engine for damage. When they won't do that - demand a buy back and buy a different product from a company that have real quality concerns about customers - and not marketing. I will try Nissan next.

This is a defect and the MFg should make good on it or pay your money back.

Bad engins can be very dangerous.

[<TMD>]

Have your dealership test the temp the engine is running at. The ECU is likely sensing a low temp as the T-stat is not operating properly and needs to be replaced.

The ECU will pump extra fuel in at low temps.

This is common on both Carbed and EFI engines..bot Mercury and Yamaha.

TMD

[LOYD]

I have a 2005 fs115 with only five hours into break-in. I've remove oil once because of making oil. I had to limp back to landing yesterday because of engine missing extremely bad. I have followed engine break-in procedure per text. Techs told me at 4 hours to start running it for extended periods at or near wot. Of course, never running at wot for over five mins. I've owned 3 other 2-stroke yamas with no problems. Making oil is definitely a problem with the fs, especially if you stay under 3k rpms.

[www.hansen-mcmlxx.gl]

Know your problems.
I solved mine, by using a better oil.
First I used 15W/40 oil, and gas ended up in my oil, and the sparkplug in Cylinder no. 1 was dirty.

Now I use the best synthetic oil, and changes oil and check my plugs every 3 month.

After changing to a better oil, I have clean spark plugs, and less gas in the oil.

My F-115 has 4 seasons on the water, and aprox. 700 hours on the meter.

Only once I have had a major problem.
The tilt-relay turned its back on me, and had to be replaced.

www.hansen-mcmlxx.gl

[viper]

I have purchase twin yamaha 100hp 4 stroke back in 2000 and have the same problem of gas entering the oil sump. I have talked to my dealers to resolve this problem. All I got was a run around. The only way I was able to resolve this problem is to shut off the engine as soon as I got to my desination. I honestly believe the thermostat is set to open much to early which would cause the engine to run much to cold in Idle. The result would be, not having the piston rings fully seat, which would cause fuel to bypass the rings into the oil. I hoped yamaha would evenually produce a thermostat that opened up alot later, which I ask and found my dealer to say: "They are not planning to! Then I thought, How about finding the same size themostat from another outboard motor company with a higher rating than what I got? Well, That was as far as it went! Maybe one of you can try this theroy and let me know. In the mean time, Change you oil!

[spert*reynolds]

just jumppin' on the bandwagon, i have a f115 with 25 hrs. it started showing signs of gas in oil with about 15 hours after a long day of *****ing. when i took it for service at 20 hrs, i asked service guys what was the story? they acted as though i was stupid and suggested i put to much oil in it, i'm checking on an unlevel surface, or i'm checking it while it is still hot. but one thing is for sure is they never said they had heard of it ever happening before. i thought for a second i'd taken it to area 51 for service. so they sent me on my way and told me to"keep an eye on it". next day i bought the extended warranty and i guess i'll just keep an eye on it.