What micron size is recommended for the primary and secondary fuel filters? Thanks
What engine? Do you have a Racor primary filter?
Our 26U has a Westerbeke 21a with a Racor primary filter.
Primary filter is a Racor 200FG.
My first thought was to use the 2 micron filter but then I read (on the internet so it has to be true 
) that the increased resistance to fuel flow could starve the engine of fuel if the fuel pump is not adequate. Westerbeke doesn’t state the micron size of their secondary filter (just ahead of the fuel pump) but I’m guessing it is a 2 micron filter since that appears to be the norm for the secondary filter.
I just replaced the fuel system on my Universal 5432 and my research and advice from an engine guy suggested that a 30 micron filter feeding into a 10 micron and then the fuel pump was tyhe way to go. This has worked well for the last 150 hours of engine use. YMMV
Blake
Procyon N33
Brentwood Bay BC
I went to a diesel seminar at a SSCA meetup years ago and the presenter said the secondary filter (on a Yanmar I think it was) was about six microns.
Bruce
Nonsuch, N30
Whitby, ON
Here’s a good article on this topic: Diesel fuel filters: Which should you choose?
Thanks for all the replies and the article Bob linked to explains a lot to me so thanks for that.