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Fuel Pumps Questions.

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Old 10-24-2004, 07:03 PM
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GLH
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Default Fuel Pumps Questions.

I have Mercury Racing engines 600SC's, I am starting to be very annoyed about the mechanical fuel pumps on my mills.

I have put new ones on both engines this spring when i started using the boat and I am not satisfied with these things... I am constantly looking at my fuel pressure and have become very tentative with fuel pressures that do not seem to be consistent at all. Why are those things so freaking flaky as to performing consistently.

Anyway I am now considering seriously electric fuel pumps with regulators.

I would like input from engine builders and knowledgeable fellow OSO'ers as I have found this is a reliable forum to get reasonable suggestions.

Thanks for your input. And have a peak at this while thinking of what set-up could put my mind at ease with the pressure on my twins!

G.L. Harvie
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Last edited by GLH; 10-24-2004 at 07:06 PM.
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Old 10-24-2004, 07:08 PM
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Default Re: Fuel Pumps Questions.

Sorry I posted this in the wrong section.

If God is watching maybe you could move it to the Tech section. Thank you.
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Old 10-24-2004, 07:27 PM
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Default Re: Fuel Pumps Questions.

hey . . as long as you post it like that . . have at it
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Old 10-24-2004, 07:34 PM
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Default Re: Fuel Pumps Questions.

as a matter of fact i think that any "off general discussion" post must be acompanied by a photo of a scantly clad female (sorry women of OSO, start a new thread )
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Old 10-24-2004, 08:01 PM
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Default Re: Fuel Pumps Questions.

GLH,

I know where you're coming from. I think I've bought every mechanical pump on the market, including the 170 gph Hardin Marine pump and my fuel pressure would still drop to 3lbs after a while at wide open. I finally decided to go with electric pumps and have been able to forget about low fuel pressure altogether. I've been running the Holley "Black" electric pumps this season. With the regulators adjusted to 9lbs at idle, I'm at 6lbs under boost.

...are you going to Miami in Feb.?

Kurt
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Old 10-24-2004, 09:56 PM
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Default Re: Fuel Pumps Questions.

same problem as glh, im always worried about my pressure. i have to get a correct pressure reading, not even sure the gauges are correct. kurt did you change the pumps yourself??? dave
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Old 10-24-2004, 10:29 PM
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Default Re: Fuel Pumps Questions.

Many people have had problems with the electric pumps burning up. Some have burned a pump up with in hours of installing it. The problem comes from them having to lift the fuel and then being dead headed. I'm running a pair of Mallory 140 marine pumps. When I first installed them, I had the pumps dead headed. These pumps had a internal bypass that was supposed to eliminate the need for one. I decided to add the bypass to prolong the life of the pump. There was a noticeable difference in the sound of the pump after the return was installed. The pump was definitely not working as hard. That was 2 seasons ago. I now have about 50 hours on the engine (about 25 on each pump) and they are needing to be rebuilt. When the tanks get below 1/2 the pumps are no longer able to lift the fuel and the pressure quickly drops to zero. As nice as the electrics may be, I'm thinking that the real solution still resides in the old mechanical pump. Frankly, I don't think the Hardin pump is a very good one. I'm not sure if Edelbrock offers a marine fuel pump, but they would be my first choice. You should be able to convert the standard 6 valve street pump to marine duty pretty easily. You just need to remove the hose bung from your current Hardin pump and install it into the new one. I believe that the hole would be 1/8" pipe.
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Old 10-24-2004, 11:42 PM
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Default Re: Fuel Pumps Questions.

You might try a Merc 900sc mech.I have had pretty good luck it. However I now run a 14 psi BG with a regulator and a return line. It is cheaper and I get NO fluctuation. Just be sure to run to return line, you can plumb is without one but you will still get fluctuations. Forget the electric.There are problems with being coast guard approved, and fire hazards which brings up the insurance issues if you ever have a problem. I have run over 1000HP with no pressure drop a all. Just my experiences.
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Old 10-24-2004, 11:49 PM
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Default Re: Fuel Pumps Questions.

do you have one way check valves in your fuel system?
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Old 10-25-2004, 12:27 AM
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Default Re: Fuel Pumps Questions.

GLH,

Have you changed your fuel filters recently? I had a problem this summer with low fuel pressure that resolved immediately with fresh filters. Also, is the fuel line from the tank to the pump sufficient size to feed the pumps? With 600 H.P., you should be running at least AN -10 size supply line to the pumps.

I feed my 650 H.P. with AN -10 lines, Racor water separating fuel filters, Holley mech pumps, and a regulator just before the carb. Might want to check with Mike @ C.P. Performance. He has always been very helpful to me with advice on this topic.

Chris

Last edited by RedDog382; 10-25-2004 at 12:33 AM.
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