nightmoves

I had low fuel pressure problems last year after installing gen V style engines.The original fuel sytem is complicated and had a bunch of 90's.I took out all The 90's and with the original black SW pump and a small(7psi) holley I had poor fuel pressure at idle, Put new holley on had 7psi at idle-took boat for a ride 21/2 psi @3500 limped in.Changed spring in pump added regulater adjusted pressure down to 7psi but would not hold it it after 5k rpm. that's behind me now i'm installing 565 ci w/ the big mechanical pumps.I have everything out except the line from the tank. Man I did not mean for this to run on like this! Question; should I still pull thru the original old SW(black pump) I think originally a T after pump returned fuel to The water seperater. I guess I need A schematic for a functional system from some of you experienced engine builders. I believe those old pumps could be the cause of this intermittent pressure situation and of course a lost summer.

custommarine

The original system used the SW pump as a supplement pump that had a tee on the fuel pump outlet side. The supply to the SW pump either came from a second fuel tank pick up or from the spare "out" port in the fuel filter. If you changed this you may have removed the one way valve. Post a photo of what you have or e-mail to me and I will try to help.
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aex

are you using a good fuel line ? fuel pump suction can collapse the line , especially where it curves , causing erratic fuel pressure .also with those big engines use 1/2 inch id hose to the pump .

Vinny P

First start by making sure that the pick-up in the tank is at least 1/2" i.d. Get rid of any brass 90* fittings, they will kill flow.

What type of pumps are you planning on running? Most run a mechanical and an electric together. #8 braided line is the minimum, most prefer #10.