Yamaha 250 four strokes making oil

[Parker28]

Anyone else having this problem? My pair of 2005, Yamaha 250 four strokes are making oil. Two oil analysis test have confirmed fuel in the oil. Changed thermostats, plugs, fuel filters, oil and oil filters at 300 hr. service. Nov. '09 did a leak down test; 2 cylinders failed on one, and 4 on the other. Treated problem with Evinrude power tune. Changed plugs, oil and oil filters. Repeated leak down test. All cylinders passed! This significantly improved the fuel in the oil problem, but it is still happening to a lesser degree. My Yamaha dealer repeated the leak down test. It passed again. The dealer and Yamaha warranty people did not recommend repeating the "decarbon" procedure with any brand of decarbon treatment, because "it could cause more problems at this point". Dealer just changed the oil, and after 8 hours, oil has climbed the dip sticks 1/4th inch. There is a faint smell of gas on the dip stick. (Before the decarb process, gas smell was stong.) And YES, I check the oil with the engines in the EXACT same position and temperature every time. At this rate, I will need another oil change by 50 hrs. I bought this 28' Parker in May 2009 with 210 hrs on the motors. There is now 418 hrs. This is a recreational fishing boat. The motors run and sound great, but the oil changes are getting old. The Yamaha warranty people and dealer agreed to pay for 2 oil changes. They also replaced an oil pressure sensor that was giving false alarms. Now, I am just waiting to see if this problem continues. Maybe increasing the "Ring Free" dose from 1 oz./ 10 gallons to 1.5 oz/ 10 gallons would help? Any comments or suggestions welcomed.

 

[sdsaw]

Re: Yamaha 250 four strokes making oil

Sounds like you are checking the right things

Possibly over-proped?

Are your RPM's reaching the upper end of the recommended range at WOT?

 

[rodbolt]

Re: Yamaha 250 four strokes making oil

that would be my next question, cant you hit a minimum of 5900 RPM with moderate trim AND a normal load.
second is, who used an evinrude product on your in warrenty Yamaha? sounds a little skanky to me.
the YEIS injection or fuel system treatment works far better.
and 3rd you MUST run that motor above 4000 RPM for at least 30 minutes on the way back in to burn off any oil contamination.
there are about 30 of theses engines at our marinia both recreational and commercial, none make oil.
however we tend to prop them correctly and educate the usesr about extended trolling and why after that you need at least 30 minutes above 4000 RPM, 4500 would be even better.

 

[Parker28]

Re: Yamaha 250 four strokes making oil

With trim tabs down and motors almost all the way down, they run 5800 to 5900 WOT. Thats 39 to 42 knots depending on wind and current. Tabs up and motors trimed up they run 6000. The Yamaha tech rode with me to check that, as well as, do a computer check of the motors. They said props were fine.

An independent boat mechanic with 25 years experience, working on outboards used the Evinrude product and did the first leak down. Yamaha knows we used "Power tune". They may not have liked it, but they did not make an issue over it. This man is an excellent mechanic. He has worked on all my boats for over 12 years now. The Yamaha dealer knows him because he buys a lot of parts there.

Unfortunately, you can't always run 4000 + rpms in a fishing boat offshore. A Parker boat will beat you to death in a 2 to 4 foot sea running 4000 rpm. I do not troll. Bottom fish only. The motors are shut off at anchor. There is some low rpm time while hunting for the next hole.

So far, the dealer and Yamaha warranty people have been reasonable. I was told by a warranty person in Atlanta that its not abnormal for these motors to have a little fuel in the oil. That was news to me.

We shall see what happens. Thanks for your input.

 

[rodbolt]

Re: Yamaha 250 four strokes making oil

trust me I know that hull.
sometimes you need to temp gun the block and heads while running at its normal RPM,one T stat can fail or stick open and the engine temp sensor may or may not detect it. two T stats and one block temp sensor.
that F250 is way way more than most Evinrude techs ever saw.
could have a vent line leaking from the VST. could be several things.
most the computer simply doesnt monitor.
I typically use the laptop to keep from chasing ghosts. if the ECU doesnt have an issue with the sensor it monitors I dont have to test it.