Another Take on Micron Size
I am not saying the following is the correct way and in fact, my friend and contributor to this forum captnron, reminds me often that it is not the correct way.
My fuel system consists of a Racor with a 2 micron filter followed by an electric fuel pump and then a 10 micron secondary fuel filter. That's the way it was when I purchased the boat and that's the way it remains.
Logically speaking, a 2 micron filter followed by a 10 micron filter defeats the purpose of a dual filtration system. So why do I leave it that way? Because the Racor on my vessel is easy to get to and easy to change. On the other hand, my secondary requires 2 contortionists, four hands, bruised knuckles and plenty of profanity to change. So I let the Racor do most of the work but I check the bowl frequently and I change it when necessary.
While I did have some issues with my fuel system in the past it was remedied by replacing the 20 or so year old electric fuel pump with a new Facet Gold-Flo electric fuel pump. In my case the 2 micron Racor does not inhibit fuel flow and my 10 micron secondary, although I change it, is never dirty.