fuel pump....running rich

[milkman250]

88 4.3 omc. My engine is suppose to have a mechanical fuel pump and someone has removed it and put an inline electric pump on it. Boat is running rich, while idiling in water I can see gas floating around boat and the back of the boat is black when I pull it out of the water. I have done a carb rebuild also and nothing has changed and the spark plugs are dry and black, on the other hand boat seems to run just fine with no hiccups and goes to wot. Could this electric pump be pushing to much fuel and causing this rich condition with all the unburnt fuel coming out of exaust?

 

[Bondo]

Re: fuel pump....running rich

88 4.3 omc. My engine is suppose to have a mechanical fuel pump and someone has removed it and put an inline electric pump on it. Boat is running rich, while idiling in water I can see gas floating around boat and the back of the boat is black when I pull it out of the water. I have done a carb rebuild also and nothing has changed and the spark plugs are dry and black, on the other hand boat seems to run just fine with no hiccups and goes to wot. Could this electric pump be pushing to much fuel and causing this rich condition with all the unburnt fuel coming out of exaust?

Ayuh,... The fuelpump should be putting out 5psi....
If by chance an Efi pump was used, the pressure will be well over 30psi....

I'd sooner think the float is set wrong, or something else in the carb is not set properly...

 

[milkman250]

Re: fuel pump....running rich

I could not find exact specs for the float. I was told to set it level, its a 2 barrel rodchester

 

[wifisher]

Re: fuel pump....running rich

But have you checked fuel pressure? As Bondo is saying, if the pump pressure is too high, the carb will overfill.

 

[milkman250]

Re: fuel pump....running rich

No have I have not, so 5 lbs is
max pressure or is their a certain range it needs to be in

 

[milkman250]

Re: fuel pump....running rich

I just checked fuel pressure, and its at 7.5psi. Is that to much and causing this rich condition. I also rechecked float and set it a little more shallow. Took boat out and still getting black all over back of boat where the water line is. I did a lot of idleing in one spot adjusting shift cables, and that's when I really get the black water lines

 

[Don S]

Re: fuel pump....running rich

Is the choke open?

 

[milkman250]

Re: fuel pump....running rich

Yes choke is disabled and butterfly tied open with zip ty

 

[RIDEPATE]

Re: fuel pump....running rich

Put a regulator on it.

 

[milkman250]

Re: fuel pump....running rich

So u think that the fuel pressure is causing the problem, the manual states pressure between 5 3/4 to 7 psi is acceptable. Is my 7.5psi pushing it over. Thanks for reply I was thinking about a regulator the other day, but get tired of throwing money at it and not getting fixed. Iv thrown so much money in the boat it
ought to sink

 

[Don S]

Re: fuel pump....running rich

Merc specs that pump should be max 7, Volvo says 6.5. If you have 7.5 (and it is an old carb and floats) you might want to replace the pump or check the gauge. I wouldn't waste my time with regulators. You have a problem you need fixed, not bandaided.
A regulator is a bandaid for a bad pump that may get worse.

 

[RIDEPATE]

Re: fuel pump....running rich

Put the mechanical back on it and ditch the electric. And a regulator will work as a diagnostic-tool......................

 

[milkman250]

Re: fuel pump....running rich

Well for the mechanical one, I guess some one put a newer block in, cause their is a cut out in side of block but no hole for the arm, and I assume if it was machanical it would have a plate over it. Sorry for the false info, I'm finding lots of miss match parts on boat, but thankfully they put all marine parts back on. Iv been looking for fuel pumps but most say 4 to 7 psi, is their any more specific to keep it around 5 psi

 

[RIDEPATE]

Re: fuel pump....running rich

Well for the mechanical one, I guess some one put a newer block in, cause their is a cut out in side of block but no hole for the arm, and I assume if it was machanical it would have a plate over it. Sorry for the false info, I'm finding lots of miss match parts on boat, but thankfully they put all marine parts back on. Iv been looking for fuel pumps but most say 4 to 7 psi, is their any more specific to keep it around 5 psi

Does it have a 2-bbl? or 4?? If it has a marine carb, the float-bowl vent runs via tubing to the mech-pump, (at least on a crusier it does). If yours has a bowl-vent in the top of the body , around center of the throat , it's an automotive carb, IMO, which can be fixed. I'd try a regulator just to see if it fixes your problem first then go from there.