3.0L OMC Running Rich

[BruceRBurley]

This seems like a site that has great information! I have a 1992 Caravelle with a 3.0 L OMC that has been giving me problems. The problem started to get progressively worse the last few times I had my boat on the water. I have a hard time keeping the engine running under 1000 rpm and black smoke is coming out of the exhaust. I did a complete tune up; plugs, rotor, cap, inline fuel filter, water canister, ect. The engine still ran like crap so I rebuilt the Holley 2 barrel carb. I replaced all gaskets and the float (center hinge). Even with all these upgrades and carb tuning the engine still runs terrible. I'm getting a tremendous amount of raw gas in my crank case. I pulled 2 gallons of oil and gas mix last night. (With the engine running, the oil/gas mix starts to surge out the valve cover breather vent). I realize this is tough on the engine. I have tested the fuel pump and get 7 PSI with gage dead ended on end of fuel line and 5.5 PSI with the gage hoooked in line to the carb and the engine running. The fuel pressure is in specification. I also get 15-20" of vacuum (out of spec?) on the inlet side of the fuel pump at cranking speed. [/LIST] I'm at my wits end trying to figure out what is causing the engine to run this rich. Is it the carb or is it the fuel pump??? I'm trying to avoid a $120.00 / hour diagnostic check at a local marine.

 

[Reel Poor]

Re: 3.0L OMC Running Rich

welcome to iboats<br /><br />It sounds like it is definately running rich. Be sure the choke flap is opening properly. <br /><br />When you did carb rebuild did you replace the float or at least weigh it?<br /><br />Be sure there is no fuel in the crankcase as this itself will cause poor running conditions as well as savier engine damage.

 

[BruceRBurley]

Re: 3.0L OMC Running Rich

I did a complete overhaul on the carb (gaskets, valve seats, power valve, ect.) I replaced the float with a new Holley Nitrophly unit. I question the effectiveness of the spring that attaches to the float arm. It doesn't seem to do much. The rebuild instructions provide no input. This carb has an electronic choke...and yes the choke flap is opening properly. Thanks for the feeback.

 

[rbezdon]

Re: 3.0L OMC Running Rich

CHeck for fuel in the clearish hose running next to the gas line from the carb to the fuel pump. If gas is in this tube the problem could still be the fuel pump even if you have enough pressure. If the diaphram leaks the fuel is pumped directly into the engine flooding it instead of letting the fuel drain from the pump into the bilge. This is what makes a marine fuel pump and carb marine. Autos just drip. By the way, a leaky diaphram also can get fuel in the oil.

 

[BruceRBurley]

Re: 3.0L OMC Running Rich

The clear hose has no fuel in it. I did a vacuum check on the inlet side of the pump and got 15-20" of vacuum at cranking speed. I think the fuel pump may be the problem. Any idea on where to get a OMC #60889 fuel pump at a reasonable price???

 

[rbezdon]

Re: 3.0L OMC Running Rich

I got mine at NAPA. They carry quite a few marins parts and there is a NAPA store in the biggest resort town on the only lakes around Chicago for a 100 miles so they do a booming boat business there.

 

[BruceRBurley]

Re: 3.0L OMC Running Rich

Well, after looking through quite a few Holley rebuild books, I was able to determine that I had the wrong gasket on the metering block. The rebuild kit comes with two gaskets; one for older Holleys that have an accelerator pump tube hole, and one for the the new Holleys that require a small hole in th egasket aroiund the accelerator pump opening. The older style gasket will cause a rich / flooding condition during operation. The engine runs great with the correct gasket in place. Thanks everyone for all your help. I hope this information is helpful to others that may run into this problem.