mercruiser 5.7 fuel mixing with oil and blowing out rocker breather

[lowmo]

Hi please help, I have an aprox 1998 5.7 mercruiser, it starts ok and runs but after about 5 minutes it dies, on closer inspection fumes are blowing out of the rocker cover breather pipes on the the carb ,the fumes to me smell of fuel and oil, when i take the pipes away from the baffle thing, on top of the carb, the engine runs fine ,but today because the oil level was showing silly high level I pumped 4 litres out but it didnt really make a difference to the level, and the oil looked very liquid , I dont think its water in there cause theres no foaming and cant see any seporation in the liquids
any ideas many thanks Dave

 

[Bondo]

Re: mercruiser 5.7 fuel mixing with oil and blowing out rocker breather

Hi please help, I have an aprox 1998 5.7 mercruiser, it starts ok and runs but after about 5 minutes it dies, on closer inspection fumes are blowing out of the rocker cover breather pipes on the the carb ,the fumes to me smell of fuel and oil, when i take the pipes away from the baffle thing, on top of the carb, the engine runs fine ,but today because the oil level was showing silly high level I pumped 4 litres out but it didnt really make a difference to the level, and the oil looked very liquid , I dont think its water in there cause theres no foaming and cant see any seporation in the liquids
any ideas many thanks Dave

Ayuh,.... Welcome Aboard,..... Which 350, 5.7l 1998 ya got,..?? Carbed, Efi, or Mpi,..??

I'm gonna Guess it might be a carbed motor with a mechanical fuel pump,..??

If so, the fuel pump diaphragm has ruptured, 'n is dumpin' gas into the base,...

Don't start it again, til ya do an oil change,... once fixed, 'n runnin', do another oil change in 5 or 10 hours,....

 

[dan t.]

Re: mercruiser 5.7 fuel mixing with oil and blowing out rocker breather

Yep, I think Bondo hit the nail on the head there, fuel polution from a bad pump.

 

[achris]

Re: mercruiser 5.7 fuel mixing with oil and blowing out rocker breather

If it has a mechanical fuel pump, it's not 1998.... Dave, what is your engine serial number?...

Chris.......