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Fuel supply

Old 08-08-2020, 06:08 PM
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Default Fuel supply

I think I am having a fuel supply issue with my new motor. The boat runs good and pulls to 4800-4900 rpms and hits a wall. Wont go any faster. I went from a stock 454 with a 600cfm holley to a to a 555 that has a 1050. The motor is around 650 HP. With the new motor it still goes about the same speed and RPM. I was expecting 5500 rpm instead of the stock motor rpm of 4800.

Currently it uses 3/8 hose for the whole system. The fuel tank lines have a shutoff valve to use one or the other? Each of these lines went into a stock merc water separator. I bypassed the water separator and it did not make any difference. I think it is starving for fuel.

My plan is to use a Tee and use both tanks to feed a 1/2 inch hose. The 1/2 inch hose will feed the pump and then out to the carb with an 8AN feed size. The pump is a 130gph mechanical pump.

My thought is the two 3/8 tank lines will give me enough flow to feed the 1/2" line and HP increase.

Currently the fuel pressure does not drop at full throttle and is between 5.5 and 8. The needle bounces really bad on full throttle so I can't tell what it is actually. It is pretty steady at idle and has 6 lbs.

Will this work? I was planning on trying this before I tear out my tanks to install 1/2 inch pickups.
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Old 08-08-2020, 06:51 PM
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where is the timing, base and and total all in @ what rpm
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Old 08-08-2020, 07:06 PM
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I have it locked out at 36 now and it sounds and runs good. I ran it with the timing curve the distributor came with and it ran really bad. The curve it came with added 24 degrees at 2000rpm. I had initial between 10-14 and it never ran well. The distributor is a DUI HEI. I have tried 2 different distributors with a curve and both ran crappy.
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Old 08-09-2020, 08:25 AM
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My plan is to use a Tee and use both tanks to feed a 1/2 inch hose.
Ayuh,..... It'll draw from the side with the least resistance, til that tank is empty, 'n then yer outa gas,......

So,.... Nope, a "T" in the fuel line won't work,......
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Old 08-09-2020, 08:57 AM
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Are you running the original prop?
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Old 08-09-2020, 10:06 AM
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Two tanks one motor is a problem trying to keep tanks level. I ran a 1/2 inch line from both tanks to 1/2 inch shut off valves and then to a tee y to my mech pump then to a by pass fuel regulator. Then I took the by pass lines to a right or left fuel valve and back to the tanks. I can keep the tanks balanced but its a pain in the ass. But you will need a by pass regulator.
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Old 08-10-2020, 09:54 AM
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How many volts getting to coil ? Seen low voltage kill top tpm by hundreds. Keep your plug gaps under .040 slso. .035 still seems to be the good after all these years.

What exhaust including design if mufflers or inserts if any ? Seen some inserts cause 600 rpm or so. Yup.

Do you have glass sight bowls in carb ? If so, video both going from idle to WOT ? This can show fuel supply issues even if fuel psi reads well. Furst saw this one a dyno way back. Ran around with a cut off head for days until I stood next to the motor covering my privates. Lol. Before gopros and smartphones. Ha.
n
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Old 08-10-2020, 12:50 PM
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What do your plugs look like after a hard run at wide open? If they have some color on them then fuel isn't the issue. If you have at least 5.5lbs of fuel pressure, fuel delivery shouldn't be the issue.
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Old 08-10-2020, 04:51 PM
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What are the cam shaft specs? Too small of a cam a540 will hit the wall sooner than a 454.
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