Gas in the Oil on 1988 Mercruiser 260

[JohnCiccarelli]

Any idea what could cause this? I was told fuel pump or carb problems. Is there an easy way to tell?

 

[HVAC Cruiser]

Re: Gas in the Oil on 1988 Mercruiser 260

How much gas are we talking about? I have seen bad mechanical fuel pumps do that, that is the most probable cause. If it is a significant amount of gas and it is dumping in through the carb the engine would flood out and not run

 

[achris]

Re: Gas in the Oil on 1988 Mercruiser 260

Dumping fuel into the oil though the fuel pump shouldn't be possible. That's why MARINE fuel pumps have dual diaphragms. If it does turn out to be the pump....Suggest you replace it with the approved type.

Chris........

 

[JohnCiccarelli]

Re: Gas in the Oil on 1988 Mercruiser 260

I am having the engine rebuilt and the machine shop says that there is a lot of gas. I rebuilt the carb and did not see anything obviously wrong. I do not see any fuel dripping inside the carb when the engine was running. I know that the choke does not seem to open properly. It is not electric and uses heat from the intake manifold.

Any ideas. Is there a way to diagnose the fuel pump that is not installed on the motor?

John

 

[achris]

Re: Gas in the Oil on 1988 Mercruiser 260

...Any ideas. Is there a way to diagnose the fuel pump that is not installed on the motor?...

John,

Just block the outlet of the pump and put pressure on the inlet fitting.... If the pressure drops, you got a hole in the diaphragm somewhere.

Chris......

 

[Don S]

Re: Gas in the Oil on 1988 Mercruiser 260

The fuel pumps do fail and dump gas into the engine, the marine fuel pump only prevents gas from dumping into the bilge, not into the engine.
If you have a lot of fuel in the crankcase, replace the fuel pump. It's the only way to get a large quantity of gas into the oil.