250 XL 3.0ltr EFI Saltwater Series.....Looks like an oil tube but not sure.

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24ANGLER

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Jul 8, 2009
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Hi Folks, Would like to put this out there to see what i can find out. I was doing some other routine maintainence on her yesterday and came across
a line what appears to be a oil line that's been cut off, it has a tie-wrap on it but cannot find the other half to it. I consider myself an advanced mechanic and work on my engine all the time but i'm lost. The location of the the tube thats cut off is (starboard side) lower block just aft of the carb assembly. Also its a threaded fitting into the block with the tube on it. (the tube is larger than the regular oil tubes gong to each cylinder. Any help would be greatly appreciated.


24Angler
 
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Texasmark

Texasmark

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wired247

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Re: 250 XL 3.0ltr EFI Saltwater Series.....Looks like an oil tube but not sure.

Its been edited out by iboats. Just give us your motor serial number and the part number you are referring to. Its probably one of the lines going to or coming from the oil tank for premix.

Did a little google fooing of the place I thought you may have looked at. Yep. Thats a check valve. Those arent oil lines BTW. They are bleed lines and they help recycle the gas and oil mix that puddles up at idle so the motor doesnt bog down. The check valves stick into ports in the manifold and block and direct the fuel back into the intake to get sent into the motor again. You more or less need all of them to be connected...more or less. Just hook up the bleed lines like outlined in the drawing.
 
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hkeiner

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Re: 250 XL 3.0ltr EFI Saltwater Series.....Looks like an oil tube but not sure.

I posted a thread a long time ago that discussed the two check valves that are involved in the Mercury oil injection system. It includes diagrams and discussion on what these two check valves do. In short... one check valve provides positive pressure to the oil tank when the engine is running so that the oil will flow (via an oil line) from the oil tank towards the fuel pump via the reservoir tank. A hose runs between this check valve and the oil tank. The other check valve avoids a vacuum in the top reservoir tank if oil flow to the reservoir tank is obstructed while the fuel pump is sucking oil out of the reservoir tank. The hose connected to this check valve is short and does not connect to anything at the other end. It only directs oil seepage from the check valve (only occurs if the valve is faulty and leaks) to a place it won't make a mess or cause other problems. Your engine may be set up differently but perhaps is similar enough to where the diagrams and discussion are of help to you. If you want to read this thread, search for "Faulty check valves on 150hp V-6 oil injection system causing smoke?"
 
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m casey stock

m casey stock

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Re: 250 XL 3.0ltr EFI Saltwater Series.....Looks like an oil tube but not sure.

hkeiner said:
In short, the most likely culprit is the crankcase 2psi check valve, which provides pressure to the remote oil tank when the motor is running and relieves pressure from the remote oil tank when the motor is shut down. If this valve is defective (i.e., provides too much pressure when the motor is running or does not quickly relieve pressure when the motor is turned off) too much oil can be pushed into the fuel lines after the motor is shut down, causing the symptoms you describe. The below link contains a much much longer discussion on the oil injection system and possible causes for too much oil in the fuel line and too much smoke.

Faulty check valves on oil injection system causing smoke?*/ 182406
Click to expand...


Twice now in about a days time there has been a reference to your old thread, I found it and read it and it is very informative. I have the oil build up under my carbs as well as sometimes the hard start after warm up and sitting. I gave neither much thought because I was told (like it was normal) to not tilt my motor all the way up for long periods of time (like overnight) because of the oil leakage. I also figured I had my motor idled down too far and that was causing the hard start (this still could be so, because I don't recall excessive smoke) where I boat at they are overly sensitive to any type of wake. So, in short it sounds like even though I didn't think there was anything left to fix on mine, maybe there is.
I was thinking you could make a comment on your old thread and bring it back to the surface (If I do it I'll be in trouble with big brother LOL) that way, with boating season coming up soon, it might be a helpful read for someone like myself, that just likes to get on here without any particular problem and read, that would not otherwise search it out. Just a Thought :) since it's such an informative thread.
 
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m casey stock

m casey stock

Chief Petty Officer
Joined
Apr 29, 2012
Messages
514
Re: 250 XL 3.0ltr EFI Saltwater Series.....Looks like an oil tube but not sure.

hkeiner said:
I posted a thread a long time ago that discussed the two check valves that are involved in the Mercury oil injection system. It includes diagrams and discussion on what these two check valves do. In short... one check valve provides positive pressure to the oil tank when the engine is running so that the oil will flow (via an oil line) from the oil tank towards the fuel pump. A hose runs between this check valve and the oil tank. The other check valve avoids a vacuum in the top reservoir if oil flow to the reservoir is obstructed while the fuel pump is sucking oil out of the reserve thank. The hose connected to this check valve is short and does not connect to anything at the other end. It only directs any oil seepage from the check valve (only occurs if the valve is faulty and leaks) to a place it won't make a mess or cause other problems. Your engine may be set up differently but perhaps be similar enough to where the diagrams and discussion are of help to you. If you want to read this thread, search for "Faulty check valves on 150hp V-6 oil injection system causing smoke?"
Click to expand...

Good read and very informative!
 
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