2019 DF300 Making Oil

[D'oh999]

Thanks Red, appreciate you lending us all your expertise, good to understand these things even though Im not going to tackle pulling this stuff apart LOL!

It seems bigger Yamaha outboards suffer a lot of this “fuel in oil” issue, I wonder if its something to do with the u-beaut cylinder coating that Yamaha introduced some years ago, you know, the stuff that allows them NOT to do ANY running in of new motors. Can run ‘em like you stole ‘em straight out of the showroom, apparently…..

The Hull Truth boating forum is awash with “Yamahas making oil” threads. Dont seem to see the same issue arising nearly as often for Suzukis or most other brands though.

On that basis I would be wary of Yamaha mechanics advising about this issue pertaining to Suzuki’s. 2 different beasts almost entirely.

Plasma Sprayed Cylinders is one of the reasons I chose Zuk over Yamaha, Warranty, Price, Timing Chain, More Oil, and Bigger Prop, the others. But from my 2 Stroke Tech days, I swore I would never own a Nikisel Cylinder Snowmobile

But, Red. I hear your explanation and understand, but I would venture to guess that Oil Dillution happens more at shut down with bleeding injectors than when the engine is Hot and Running. Hot Gasoline, becomes a vapour, Hot engine has tighter Rings, including the Oil Control Ring, with tighter tolerences. And a Running, Hot Engine has Postive Crank Case Ventalation, Vacuum, sucking Gasoline Vapours out of the Crankcase.

[redlowrey]

If you had injectors that leaked after shut down you would have starting problems especially after a hot soak, and with closed loop engines there would be a change in the fuel trims.

[Makeitdo22]

Looking forward to the resolution on this one. I have a similar "making oil" problem on my 2015 DF225 w/ 274 hrs. Best of luck for a positive outcome.

[Triton2300]

Update. This spring the marina changed my thermostats and oil. Thermostat part number 17670-90J21. After warm up these thermostats read between 153 and 159 cruising (4000 to 6300 RPM). They never drop below 138.
The old thermostats would run 10 to 15 degrees cooler.
I have 15 hours on the thermostats and oil change. Oil level has not moved. Hopefully we are good. At 20-25 hours I am going to submit a sample to Blackstone Labs for analysis.
Hopefully the new thermostats corrected the issue.

[Triton2300]

Update. Results from Blackstone Labratories on Fuel Dilution is at 2 percent. 25 hours on the oil. The changes to bring it into the safe zone have been thermostats changed and going to Yamaha FC-W 10W30 oil. The other thing that I had done differently was to draw my oil for analysis when the engine was cold. This may have skewed the numbers a little. Blackstone said to make sure I run the engine as I normally would for at least 30 minutes then take the sample. This may give better results because it will burn off excess fuel in the sump before I sample. I will run another sample this fall at around 50 hours so things are looking pretty good.

[Triton2300]

Blackstone oil report on my DF300 (58 hours running time on oil) came in at 1.3 % fuel dilution. I bought the oil extraction kit from Blackstone so I could remove the sample while the oil was hot.
The new thermostats seem to have corrected the problem with the engine running in the 150 degrees F range.
I had the engine winterized. I also changed all the anodes, spark plugs, oil and filter, lower gear oil, and low pressure fuel filter. Ready for the spring.

[Triton2300]

Blackstone Oil Analysis (60 hours running time on oil) Fuel dilution 1.8 percent. Engine runs between 150-160 degrees F. Good report!