I'm switching from an electric to a mechanical pump, and I am wondering if I should run my line from the tank to the fuel/water separator first and then the pump, or go straight to the pump. I believe it went to the filter first when I got the boat and it had a mechanical pump on it. When I went to an electric pump I ran the line straight to the pump because I understood that those pumps are designed to push fuel rather than pull it, but I believe the mechanical pumps are a different beast. Does this make any difference? It would seem to be a good thing to have a filter in place ahead of the pump as long as it can pull the fuel through it without any problems. FWIW, it is one of the Holley 6-valve pumps through 1/2 inch lines.

my vote is filter first.it keeps any trash from entering the valving in the pump.

Merc runs them after the mech pump stock, crazy I know. However, that filter is not much of a filter with a high micron number, it is really more for water.

not...merc sucks fuel through the spin on fuel filter..carb models have a rock filter in the carberator also..(Qjet) i have also seen some efi with and with out in line fuel filters after the feed pump..

Most Merc fuel/water filters are 4 micron, which is pretty fine. I use a 100 micron filter before fuel pump.

with electric pumps: Separator, filter, pump, then another filer right before the carb.

[ATTACH=CONFIG]541711[/ATTACH]

Bud. I know for a fact that Holley fuel pump will pull at least 762hp worth of fuel through a stock Merc filter head/filter and a 3/8 hose with a little tiny pick-up tube and a whole bunch of NPT 90's all over the place. Not my setup but have been on the boat many times where it went to WOT and stayed there for 15-20 minutes at a time.

Best to pull fuel through the seperator as opposed to trying to push fuel through the filter .

You have been misinformed, the spin on filters from Merc are 10 micron. The inline EFI fuel filters are 4 micron

Well crap, then why am I going through all the trouble to install that larger pickup and 1/2 inch hoses? Oh well, going to do it anyway just in case.