Fuel pump oil injection

[BadBear603]

I have a 1988 Merc 90hp, 3 cyl, 2 stroke. It has oil injection. I have a 22 gal Moeller tank under the bench seat. I was having problems with the motor and noticed the fuel pump was leaking pretty badly. I ordered a new fuel pump. It was an aftermarket one that was pretty useless but I used the gaskets & diaphragms to rebuild the existing pump. I ran the motor but still had problems bogging down under load. I found a lot of water at the bottom of the fuel tank. While installing a fuel/water separator I had to cut the old fuel line. I noticed oil in the gas all the way from the motor back to the tank. (None in the tank, pure gas). Is this normal? For oil to “backflow” from the motor? I don’t recall any oil in the few drips of gas when I disconnected fuel lines in the past. Thanks.

 

[airshot]

See that happen on my 1992 classic if I leave the fuel line connected to the engine. Over time I will see the clear fuel filter which is just a foot from the fuel connecter begin to turn blue from the oil. I returned to my old habit of disconnecting the fuel line from the engine when I load the boat onto the trailer. Never been an issue for me. Just figured oil from the pump running back into fuel line..

 

[Faztbullet]

Make sure the diaphragms are correct as got to have the 2 large holes in rubber. If not you will not mix oil with fuel

 

[BadBear603]

View attachment 391027

Make sure the diaphragms are correct as got to have the 2 large holes in rubber. If not you will not mix oil with fuel

Thanks Faztbullet - yeah that was the problem with the after market diaphragm. It did not have holes so I cut them myself.