Yahama F115 4 Stroke - Gas in oil Issue (Again)

[Eagle180]

Lots of folks know about the 'making oil' issue on 4 strokes and if not, you can search this forum for a little light reading.

My problem was that my Yahama was making oil and the dealer changed the low pressure fuel pump which seemed to help a bit. However, oil level continued to rise, therefore, Yahama told them to change thermostat which they did. Oil level continues to rise but not as much.

I talked with Yahama and they said that if the rings are not seated 100% and since 4 strokes run cooler that if your running the engine at 3000 rpms or less, then you will get fuel blow-by thus increasing oil level in crankcase. They said I should de-carb the engine using their YIEC solution which I am waiting on my dealer to get in.

So, I tested this theory as best I could. I've been trolling for White Bass and Stripers and have measured oil level before and after... these trips were idle troll for about 2-3 hours, then I run the boat over 5000 rpms for about 20 minutes or so, put boat up and go home. The oil level rises anywhere 1/16 to 2/16 of an inch. On a test trip, I ran the boat for a good solid hour to hour and 15 minutes at WOT only, no trolling and measure oil level before and after.. no rise in oil level... GOOD!

I'm not going to give up trolling, so at what point does the oil become too dilluted that I should start to worry about proper lubrication and change the oil? Right now, since last oil change the level has risen from halfway pt. on the dipstick to almost full mark on the dipstick. This was about 15 hours of motor time.

Also, here in the south the Yamalube 20W-40 is recommended, but expensive... can I use API SL or SM 10W-40 from Wally world in order to save money on these frequent oil changes? If not, which oil would be your recommendation? By the way, motor is still under warranty until 2014.

Long post, but any info would be appreciated.

Thanks

 

[pine island fred]

Re: Yahama F115 4 Stroke - Gas in oil Issue (Again)

Same problem, same motor. I was over propped. Went from a 13 X 19 to a 13 X 15 and that fixed the problem. Max rpm was 5200, now it will spool up to 6200. Makes you wonder though, WHY? Been operating 4 strokes since the early 60s, all different displacements, compression ratios from 6.5 up to 10 to 1, carbed and fuel injected. Most of them were manual transmissions which I have always had a habit of lugging. Never had an oil dilution problem. One time I did have a fuel pump leak into the crankcase.
At any rate, what is so different/ special about this engine that causes them to bypass fuel when others dont. Only difference is that I cruise at 3400 rpm and normal road rpm for me is around 2400. Something going by the rings? Whenever I had bad rings I was using oil not making it. FRED

 

[Eagle180]

Re: Yahama F115 4 Stroke - Gas in oil Issue (Again)

I believe my prop is good, since my WOT is 5800-5900 RPMs with me, fishing gear and full tank of gas... and Yahama tech said that was good.

The Yahama person I talked too works for Yahama Motor division and said that all 4 strokes are going to get some fuel in the oil due to the fact that outboards run cooler than a car engine and the combustion chamber is not getting hot enough to burn 100% of the fuel if you are running at what they consider low RPMs which is 3000 or less! When I'm not trolling or coming up to my fishing spot.. basically running from place to place or cruisin, I run the boat at about 3500 RPMs. It is an Eagle 180 G3 aluminum boat and the motor performs great.

Why, is the question? Do Mercury, Suzuki 4 Strokes have the same issue? If not, is this a design flaw? I just can't believe I'm going to have to deal with this issue forever! I don't have this issue with car engines which run alot lower RPM on the road with the cruise control set... don't have to break-in those engines for 10 hours!

Once the oil level rises, I don't want to just drain some of the oil out to bring the level down, especially since I feel the gas has diluted the oil which in turn is going to compromise the lubrication of the internal engine components!

My dealer has performed a leak-down test which came in below 10%, the fuel pump is good now, the thermostat is supposedly been changed to a hotter thermostat. What else is there?

 

[pine island fred]

Re: Yahama F115 4 Stroke - Gas in oil Issue (Again)

Something else occured to me today. At the same time I changed my prop, I began making sure I turn my fuel supply off. I do not have an anti-siphon valve if it makes a difference and my tank is not directly vented as you might think. If I go to add fuel before going out, the tank is always pressurized, just like the hissing when you go to gas up your car. Was never able to confirm it but I had a thought that the pressurized tank was forcing fuel into the motor somehow and the fuel winding up in the crankcase. If your motor just makes oil when operating, forget everything I have just mentioned, but if it does it while shut down, considering leaving the gas cap loose overnight or when stored.
Let me go on. The fact that a higher temp thermostat was installed is a band aid. The idea here is a hope that the higher operating temp will help boil or vapor off the gas in the oil. Nothing new there. Old radials that used 40W had oil dilution solenoids that diluted the oil in anticipation of cold weather starts. This is an EPA 3 star emissions engine. The unburned fuel gets past the rings but not out the exhaust ???? At a lower RPM you are introducing less fuel plus it has more time to burn. Only difference I can see that operating at a higher RPM would be the production of more heat which would help vapor off the gas in the oil.
I remember only seeing it mentioned once, might have been a RODBOLT post, that there was a situation where the ring end gaps were not staggered on the pistons correctly which might have caused the oil dilution. Would not surprise me if there were some defective casting of blocks or accessories that slip thru the manufacturing process causing fuel to be introduced into the lubricating system either past the rings or in the oil scavenge system. Could be that the percentage of these problems are so small that YAMAHA figures they can live with it. Since you have an extended warranty, would be interesting if you would post follow ups on your problem.
YAMAHA has a good reputation on service, that is why I bought a few. But manufacturers will try to slip things by. Good example is CHRYSLER. Numerious sights on the net stating a V6 service bulletin said that 1 qt. of oil consumption per 1K miles was normal on a newer engine. Lots of people complained that the oil pressure light came on, followed by an engine failure. It was the owners fault, not covered by warranty. Only people buying there products now are govt. agencies and rent a car cos. FRED