1989 3.0 Mercruiser. Am I going in the right direction?

[02torched]

I have noticed a decent amount of oil on top of the engine and carburetor. Its difficult to see where it is coming from however there appears to be oil sitting on top of the flame arrestor and the lip of the carb. There is also oil on the valve cover ect. From searching here it appears that the two usual culprits are either the vent coming from the valve cover caused by compression leaking into the valve cover or if the mechanical fuel pump has a pin hole in the diaphragm it will send oil through the sight tube into the carb. With the engine warm I did a compression test across the 4 cylinders and the were all reading 146-147psi so would this indicate that the oil is not coming from the vent? I have a new fuel pump being delivered tomorrow so hopefully that fixes the problem. If it doesn't what would my next step be? On a side not this past weekend I was out on the water I was heading back to the dock the boat started flooding out. I had to limp back to the dock. Any advice would be greatly appreciated.

 

[Don S]

Re: 1989 3.0 Mercruiser. Am I going in the right direction?

I have noticed a decent amount of oil on top of the engine and carburetor. Its difficult to see where it is coming from however there appears to be oil sitting on top of the flame arrestor and the lip of the carb. There is also oil on the valve cover ect. From searching here it appears that the two usual culprits are either the vent coming from the valve cover caused by compression leaking into the valve cover or if the mechanical fuel pump has a pin hole in the diaphragm it will send oil through the sight tube into the carb. With the engine warm I did a compression test across the 4 cylinders and the were all reading 146-147psi so would this indicate that the oil is not coming from the vent? I have a new fuel pump being delivered tomorrow so hopefully that fixes the problem. If it doesn't what would my next step be? On a side not this past weekend I was out on the water I was heading back to the dock the boat started flooding out. I had to limp back to the dock. Any advice would be greatly appreciated.

The fuel pump has nothing what so ever to do with the oil problem. That clear tube is for gas to go to the carb instead of the bilge if the fuel pump diaphragm ruptures.

There should be a hose from the valve cover fitting to the flame arrestor for the vapors that come out of the valve cover. Some oil is normal, and why the hose. It keeps things clean. The oil vapor does have oil in it. Cars used to have a hose/tube that put those vapors on the road under the car and off the engine. What you are seeing with the oil probably means the hose from the valve cover to the flame arrestor is missing.

 

[02torched]

Re: 1989 3.0 Mercruiser. Am I going in the right direction?

The fuel pump has nothing what so ever to do with the oil problem. That clear tube is for gas to go to the carb instead of the bilge if the fuel pump diaphragm ruptures.

There should be a hose from the valve cover fitting to the flame arrestor for the vapors that come out of the valve cover. Some oil is normal, and why the hose. It keeps things clean. The oil vapor does have oil in it. Cars used to have a hose/tube that put those vapors on the road under the car and off the engine. What you are seeing with the oil probably means the hose from the valve cover to the flame arrestor is missing.

Thank you for your reply Don. While I don't dare doubt that you know what you are talking about there are numerous posts on iboats addressing this issue and a lot of people seem to disagree with you that a fuel pump with a leaking diaphragm could not cause the oil to mix with fuel and end up all over the carb via the sight tube.

The hose to the flame arrestor is present an connected btw. I am just hoping that the fuel pump fixes the problem.

http://forums.iboats.com/mercruiser...blow-mercruiser-470-a-267860.html#post2127213

http://forums.iboats.com/mercruiser...me-arrestor-1990-mercruiser-4-3-a-331530.html