I have a 2000 502 mefi 3 with a m3sc procharger setup. the boat is new to me this year, and I have had issues with the fuel pressure going to high on me since ive had it. With the ATI boost referenced fuel regulator, it had very inconsistent pressures and would sometimes go up to 70-80lbs+ of pressure. I replaced this with an Aeromotive regulator followed by a Bell boost referenced regulator and have had similar problems, including where I can't adjust it below 70lbs of pressure even at idle. I'm now pulling the engine for a rebuild and want to have this working correctly when it goes back in....

Attaching a diagram of my current setup. I realize the return from should be run back to the tank and not the input to the pump, and will change that, but don't believe thats causing my current issues. Hoping eddie young, articfriends, or anyone else will have some ideas for me.

get rid of that boost-referenced regulator and tune the mefi3 for boost. Done. You'll never get the Bell regulator, or any other boost-ref for that matter, to remain consistent. Been there...did that.

Griswald- thats not a bad idea, however I can't even get the aeromotive regulator with no boost reference to maintain a constant pressure. Seems like there is something else going on. At one point i ran a return line directly from the Aeromotive Reg Return port back to the tank and the pressure was still 70lbs with the adjustor all the way out.

The issue is that it's returning to the suction side of the pump. I have been running boost dependent regulators with a returned system for a few years now and it's always the same. I have dash mounted fuel pressure gauges so I look at them all the time.

Where are you taking pressure?
By your diagram, there is no regulation to what you're referring to as the end port. If that's straight out of the pump that seems like an issue to me.

FWIW - I ran the return to the inlet of the pump for years without issue. Not saying a return to the tank isn't the right way to do it, but certainly not causing the issues you describe.

Fuel pressure sender on the port of the Aeromotive 13101. Verified the gauge with another fuel pressure tester, was within 1lb

I edited my post - re-read

Mine was never super consistent with it looped back they to the pump.

I see what your saying about the "end port" line, that was one of my concerns, I'm not sure if that's correct or not. There is two ports on the fuel rail- the "end port" i referenced is being fed by a small hose directly from the A1000 supply end. The "middle port" is being fed from a bigger supply line from the A1000 supply end, with it being T'd off at the cool fuel with return to the regulators. I've read Eddie Young post saying you should be supplying both ends of the rail- should both of the ports be supplied from the big line that runs through the cool fuel box then?

I agree return to the tank is best and I will fix that, but I already tried this and still had high and inconsistent pressures. I ran a hose directly from the Aeromotive Reg back to the tank just to test this.