How much fuel pressure for 502 withDemon 850?
11-21-2013, 07:15 AM
#11
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iTrader: (1)
If the carb has been flooding several times make sure you do not wash down the cylinder walls with gas. I had the same problem this spring to much pressure 8.5 to 9.0. Put on a regulator solved the problem.
I checked compressing on engine at the end of the year and it was down to 50psi on all cylinders. Both engines are out of the boat and waiting for me to tear the one down. I am guessing since the engines only have 80 hours on them, the rings are not sealing because the gas washed the oil off.
I checked compressing on engine at the end of the year and it was down to 50psi on all cylinders. Both engines are out of the boat and waiting for me to tear the one down. I am guessing since the engines only have 80 hours on them, the rings are not sealing because the gas washed the oil off.
11-21-2013, 11:45 AM
#12
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Exactly. You need enough fuel psi to fill the bowls when the float drops, and not too much to push the needle off the seat when the float is at its correct height. More psi will get you nothing as far as performance in this application. Volume is the key.
Holleys current marine pumps, are available in 110GPH, and 130GPH. The 110GPH will not require a regulator, and the 130GPH will. The pumps visually look the same, both having 3/8NPT in/out. I wish they
never stopped making the ones I use. Which are the older six valve pumps. These pumps are much better, have 1/2NPT in/out, preset at 6.5psi, and do not require a regulator. Mercury used these pumps on the 800 and 900sc engines. You can still get them, but need to modify them if you want to "marinize" them with the vent tube.
Heres the current holley pumps
http://www.summitracing.com/search/p...%20fuel%20pump
I attached a photo of the pumps I run that holley no longer makes.
[ATTACH=CONFIG]512861[/ATTACH]
Holleys current marine pumps, are available in 110GPH, and 130GPH. The 110GPH will not require a regulator, and the 130GPH will. The pumps visually look the same, both having 3/8NPT in/out. I wish they
never stopped making the ones I use. Which are the older six valve pumps. These pumps are much better, have 1/2NPT in/out, preset at 6.5psi, and do not require a regulator. Mercury used these pumps on the 800 and 900sc engines. You can still get them, but need to modify them if you want to "marinize" them with the vent tube.
Heres the current holley pumps
http://www.summitracing.com/search/p...%20fuel%20pump
I attached a photo of the pumps I run that holley no longer makes.
[ATTACH=CONFIG]512861[/ATTACH]
11-21-2013, 01:59 PM
#13
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iTrader: (3)
I run a Clay Smith pump 1/2" in and out has to be regulated just run an enderle pressure relief valve on return to the tank $60. The pump pumps like a garden hose. I know this very well cause I didn't have the fuel line hooked up and cranked the motor and washed the bilge down with fuel :-) but I was very impressed how much fuel the thing dumped all over the place...
Ive had good luck with the preset pumps in this style. The move a ton of fuel, and one less thing to screw with. I believe the self regulated ones were rated at 120GPH, and ones requiring a regulator, 130GPH.
