Fuel pessure issues with HP 500
 

Anyone have any suggestions on how to boost fuel pressure on a sea pump driven fuel pump. 98' HP 500 with BM 250 running stock 800 carb @ 4 to 5 lbs boost. This is for a friend of mine, he tried the Carter HV pump bottom switch with the stock top. Didn't seem to make any difference for the better , actually was worse. Others have suggested adding an inline or paralell electric pump. There dosen't seem to be any aftermarket bolt on mech pumps available either.

that would be a good question for Bruce, i'm sure he would know that, maybe he will drop in on us

Undersize fuel lines. ......Original fuel water separator has 3/8" fittings. Change over to one with 1/2" fittings.

The HV pump is more than enough, specially for a single 800.

It may be the pump. I am having the same problem with the same pump. I have all 1/2 fuel lines. I had 5 pounds of fuel pressure then added a holley red pump as a feeder pump and got it up to 6 to 6 1/2 pounds of pressure. I think I may go back to the SX pump which worked great.

Fuel Pressure
 

With a blower you should run about 7-1/2 to 8 lbs of fuel pressure at wide open throttle. Holley makes a mechanical pump that puts out 130 + gallons per hour.you need also to add their pressure regulator. The other options is to blank off the mechanical pump area and add an electrical fuel pump plus regulator. Use all 1/2" lines and fittings. The electrical set up is more reliable.

The culprit could also be the little cam inside the body that actually drives the fuel pump. The pump actuater would not be getting full movement then and not supplying enough fuel to give good/adequate pressure/volume. I had this on a HP500 before, took a while to find it.