I plan on re-doing my fuel system this spring. I want to add an electric fuel pump (or two), a two port fuel pressure regulator (or two single port regulators). The problem I'm having is that most of the higher end fuel pressure regulators require a return line to be ran back to the top of the tank. It's something that I'm hoping to avoid installing if I can (I really don't feel like taking out all of the seats and picking up the floor). But I didn't know if this is something that may already be installed?

Do boats generally have a fuel return line already installed that goes back to the top of the tank, or is it something that I would have to run myself?

Any advice on how to alter my fuel system would also be greatly appreciated. I understand some of the pros and cons of a one pump system (if its dead, I'm dead in the water), but if I go two pump system I can probably jerry-rig it to get me home on one pump.

First off, carb or EFI?
Second, why do you want to use electric pumps?

Carb. I just want to go with something more efficient and that can handle higher Hp if I end up building a set of 496's. The more I get into it, the more it looks like I'm going down that road...

Merc uses a mechanical pump on their carbed 1000hp SC motors, capacity is not a problem.
USCG regs dictate safety and burn time for pressurized fuel systems. Probably because of that, all marine engines have fuel systems as part of the block assembly. It would be too difficult to certify a system for every make of boat if mounted separately. Merc dead heads all their systems, no return line, even on EFI motors.
I've seen plenty of aftermarket electrical fuel pump systems, some even with return lines. It's generally not needed, adds complexity, costs, and safety issues.
My suggestions:
Go with a block mounted mechanical pump for Mark 4 motors, water pump mounted for Gen 5+. Upgrade with higher capacity marine pumps if you want.
If you go electric, Mallory makes a 110gph electric that doesn't need a regulator. I've found them to be very reliable if mounted correctly. Use an oil pressure safety switch and good lines.
My $0.02

I'm not sure if this set up would work out for you or not, But it's worth keeping in mind. See the link below. Good luck.

http://www.offshoreonly.com/forums/d...installed.html

I run an Aeromotive SS Series Marine fuel pump and a Holley fuel pressure regulator to a Holley 850. No return line used or needed. You'll need a pressure gauge to make sure everything is hunky-dory and I also run the electic pump off the ign circuit with a seperate switch and have wired it through the kill switch as well so the pump dies with the ign.

I was thinking of running either one aeromotive eliminator marine pump (one pump for both motors) with a dual port regulator, but I think I'm going to run individual holley black pumps if I decide to switch everything over.

To me it seems worth it just to have gas at the carbs when you go to turn it on (no cranking the motor to get fuel up to the carbs.). My boat doesn't hard start or anything, but I don't even like the 3-5 seconds it takes to start up. My race car had an MSD igntion with an electric fuel pump. That thing would fire as soon as I turned the key. It was almost scarey instant.

I would avoid the Holley pumps. I had one, it didn't. Several others have had them and the reviews for the most part aren't great, MSD Marine ignitions have a similar reputation. I know what you mean about the crank start up though, mine's instant!

simply run the bypass from the regulator back to the inlet of the fuel water seperator. There should be a plugged port there. Done

Hmmm, holley electric pump, MSD ignition.....bring a paddle.