Fuel Pressure Qusetion
 

I have Hawk 525 SC Carbureted motors. I'm new to this configuration. Both motors are running great and have Idle fuel pressure of 7lbs. When creating boost one motor increases fuel pressure with the boost 1lb per PSI of boost the other remains constant. It has Holley Fuel Pumps, regulators and a 800 CFM Carb on a Weiand 174 Blower with 5lbs of boost. I'm thinking that fuel pressure should increase equally on both motors. My only experience with a blower motor was a ProCharged and Injected motor with an Aeromotive pump and regulator and I know that was the case.
This was on a first drive and shake down run. I just bought the boat. It did not act like it was starving for fuel at al,l both motors were equal in RPM and power, that said I immediately got out of the throttles until I could check it out. What should I be looking for on this set up?

Most carb needle and seats can't handle over about 8# of fuel pressure and 7# is plenty as long as you flow enough volume.
I see no reason why you would want or need more fuel pressure on a carbed SC engine.
Unless the fuel pumps have sort of boost referenced interface, I'm not sure why one is going up to 10#.

That is exactly what has me confused. I'm going to check tomorrow for a vacuum boost connection and check things out in general.

You do not want fuel psi to raise on your roots blower set up since the fuel bowls remain at atmospheric pressure.

If a blow thru then you do want the fuel psi to raise 1:1 with boost to keep the float bowls same psi delta.

Anyway - since it is raising psi you have the regulator connected to a intake vacuum source. You do not want this. It should be connected to atmospheric pressure.

Like I said one side is doing this and not the other so I am going to check for a boost line if not my assumption will be a bad regulator or something blocking it inline allowing RPM to increase PSI past that desired.

Just checked the regulators, they are standard Holley with no boost. I will probably just replace both and be safe.

Does anyone know the Merc recommended fuel pressure for this setup? 525SC Carbureted.

A Merc 525SC uses a 1050 Dominator carb. Pretty sure its 5-7#.

Thank you