Gas in Oil

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   I hate to admit this, but I just finally pulled the boat out of storage last weekend to clean it up, perform some routine maintenence, and get it ready for the lake this weekend.  Here's the problem...

It's a 1990 Sport Nautique with the 351 PCM.  I warmed the engine up enough so that I could get the oil changed.  Oil pressure was pretty low and when I drained the oil I found that it had a significant amount of gas in the oil.  I'm guessing I drained about 8 quarts out, so there was probably around 3 quarts of oil mixed in.

Unless I'm overlooking something, the only way for fuel to get into the crankcase is through the fuel pump or the carb.  I would have expected if I was getting that much fuel through the carb into the cylinder and past the rings it would be running like crap.

That said, I had planned to swap the fuel pump and keep a close eye on things.  I was surprised to find a fuel pump that doesn't look much like the mechanical fuel pumps I'm used to seeing.  It appears to have three cavities and a vent from the top cavity up to the clean side of the air cleaner.

Are these pumps prone to failure?  What's the difference between this marine pump and what I'm used to seeing on automotive applications (besides the extra $50)?  Are there other things I should be looking at in terms of probable causes for gas in the oil?

Thanks in advance for any help you guys can offer.

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gtxj Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: June-26-2007 Location: United States Status: Offline Points: 9	Post Options Post Reply Quote gtxj Report Post Thanks(0) Quote Reply Topic: Gas in Oil Posted: July-14-2010 at 1:50pm
	I hate to admit this, but I just finally pulled the boat out of storage last weekend to clean it up, perform some routine maintenence, and get it ready for the lake this weekend. Here's the problem... It's a 1990 Sport Nautique with the 351 PCM. I warmed the engine up enough so that I could get the oil changed. Oil pressure was pretty low and when I drained the oil I found that it had a significant amount of gas in the oil. I'm guessing I drained about 8 quarts out, so there was probably around 3 quarts of oil mixed in. Unless I'm overlooking something, the only way for fuel to get into the crankcase is through the fuel pump or the carb. I would have expected if I was getting that much fuel through the carb into the cylinder and past the rings it would be running like crap. That said, I had planned to swap the fuel pump and keep a close eye on things. I was surprised to find a fuel pump that doesn't look much like the mechanical fuel pumps I'm used to seeing. It appears to have three cavities and a vent from the top cavity up to the clean side of the air cleaner. Are these pumps prone to failure? What's the difference between this marine pump and what I'm used to seeing on automotive applications (besides the extra $50)? Are there other things I should be looking at in terms of probable causes for gas in the oil? Thanks in advance for any help you guys can offer.

8122pbrainard Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040	Post Options Post Reply Quote 8122pbrainard Report Post Thanks(0) Quote Reply Posted: July-14-2010 at 2:14pm
	No name, Get the new pump and make sure it's a marine for safety reasons. With that much gas in the oil, the diaphragm is ruptured. Actually in a marine I think there are two diaphragms. If the other one goes, you get raw gas back up to the carb via the clear tubing and not into the bilge creating the safety issue. BTW, that's not a air cleaner sitting on top of the carb. It's a USCG required flame arrestor. (hopefully you don't have a air cleaner on it! )
	54 Atom 77 Tique 64 X55 Dunphy Keep it original, Pete <

Gas in Oil

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