I have a 502 mag with a Vortech supercharger. Yesterday while running boat starts loosing power and I look and fuel pressure and its down to about 25psi, motor struggles but gets me back idling to the launch. It turns out the ground wire terminal from the Vortech add on pump has come off and I am running on only the original merc pump.
I am wondering if the add on pump is restricting flow by being in series with the other pump if the add on is not running. Not sure why pressure would be so low unless the pump is bad or the fuel flow is severely restricted by the non running pump.
I am going to try and by pass the add on pump to check psi and flow amount. Does anyone know what the fuel pressure should be and the fuel delivery amount should be on an original 502 MPI pump.
If the pump is bad Looking for suggestions for a replacement, Buy from merc or aftermarket?

If the pumps are in series then if either pump dies it will effect the overall flow. Two things to consider with HP marine applications, is the pump is above the fuel level not below and the pump is going to run hard in an enclosed space so watch heat build up.

Looking for fuel pump testing procedure with flow and pressure amounts. 2000 502mag MPI.