GAS in the OIL???????

[Pas Bon]

We have had chronic problem with the fuel injected models. We run several 115's 200's and 250's all fuel injected 4 strokes and they ALL get gas in the oil (Crank Case)our mechanic changes the T-Stat and says to run synthetic because conventional oil is causing carbon on the valves and the fuel is coming in the exhaust valves (I think it wasthe exhaust valve anyway) but they all do it and it is a dissapointing to have this many problem and Yamaha has not addressed it!

ANybody else seeing anything like this?

 

[Silvertip]

Re: GAS in the OIL???????

This problem has also been discussed to death. Do a search on "making oil". One issue that's been discussed here is that all of your engines may be over propped, meaning they have a prop that prevents the engine from operating at the high end of its RPM band so they are "lugging". The other is doing too much idling without giving the engine a good workout after that so they reach operating temperature and burn off the contaminants. If you are developing carbon problems, run a few tanks of fuel with a high concentration of SeaFoam in the fuel.

 

[JB]

Re: GAS in the OIL???????

Running synthetic oil makes it worse, Pas Bon. As Silvertip says, be sure you are propped for max rpm with a light load, too.

See the article in Engine FAQs on "4 strokes making oil"

 

[Pas Bon]

Re: GAS in the OIL???????

Running synthetic oil makes it worse, Pas Bon. As Silvertip says, be sure you are propped for max rpm with a light load, too.

See the article in Engine FAQs on "4 strokes making oil"

why would the synthetic make it worse?

 

[rodbolt]

Re: GAS in the OIL???????

it needs to be propped so it can turn 6000 with the load you have that day.
if not its lugging and will make oil.
check the block temp, stuck thermostats make oil.
finally those engines need to be run in the 3500-4500 RPM band for at least 30 min during the return home, especially after extended trolling speeds.