dmaxx3500

im dressing the engines for my 42' cig revolution, my fuel sys is tanks to mech fuel pumps then 1' to comp electric fuel pumps to regulaters and small billet fuel filters then 1' to 1050 dominater carbs,my question is ive had drag and road race cars and never run setups like this,,this seams like the wrong way to do this,shouldn't it be run with mech pumps or electric pumps sepretly ,but not in this combination,anybody know the right way to run this and straighten this mess out

obnoxus

Merc MPI motors are the same way,,, mech pump feeds the efi pump

Chris Sunkin

If you add in check valves, you can run the mechanical on the engine, then the electric feeding it as well as a route around and straight into the regulator. If one goes, the other will continue to feed the engines. I would definitely recommend plumbing in a bypass regulator as close to the carbs as possible. If you use an Aeromotive pump, it's probably unneccesary to use an engine-mount pump- they're very reliable.

dmaxx3500

yes ,but these electrics are regulated down to 6-8lbs,so it doesen't make sense to me and should be a big restriction shouldn't it be?

Chris Sunkin

Don't know what you mean.

dmaxx3500

sorry chris we posted at the same time,i was answering the post by obnoxus,,my thoughts are shouldn't the mech pumps feed these engines good enough?,and wouldn't the electric pumps just be a restruction[with the regs and small billet filters],,id like to clean up this seaming mess or im i missing something as to make this boat run and not to starve for fuel?

Chris Sunkin

Mechanical pumps are not as consistent or reliable in their output. On an EFI in a boat- compare to an automotove EFI- the pump is in the tank which keeps it cool and provides fuel supply. Those pumps don't draw well with resistance whereas a mechanical does. In that setup, the mechanical is providing a volume of flow at fairly low pressure to the EFI pump which operates at significantly higher pressure. In a carbureted application, pressure is less important than volume, although volume is a component of pressure- low pressure equals low volume. Too much pressure and you overpower the needle and seat causing flooding. That's why a regulator at the carb is so important. You keep the pressure up to have good flow through whatever restrictions your system has, then drop the pressure right before the carb. In your plumbing, you need to make sure there are no angle fittings anywhere. Use "sweep" fittings if you have to- the one's with curved tubing. 45's and 90's are flow killers. Run larger diameter and neck down as close to the carbs as possible.