Putting aside any requirements for the lift pump screen, at least two filters in series are recommended for marine applications, with one filter being capable of removing water.  The general reason for multiple filters is to allow for staged filtering.  Staged filtering is designed to allow for very small particles to be caught while minimizing filter blockage.  Coarse filters intercept the fuel first, blocking and holding particles that would quickly fill and block fine filters.  This is a very common practice in the industry as it allows for free flow to the lift pump with moderate pleat contamination and allows fuel under pressure to be forced through the fine filter element even with high pleat contamination.

My recommendation is 30 micron on the suction side and then 10 micron for the engine spin-on.  A three filter system would be 30-10-2, deploying the 30 and 10 on the suction side, in that order.

Josh,

You will be adding a lot of work to your lift pump. These engines are designed to run on the main on-engine filter which is (per Westerbeke's Joe J.) 15-17 micron. On boats we add a primary filter to add water removal and another layer of protection. Unless you have a common-rail diesel there is no need for a 2 micron filter and it usually only leads to other problems.

Westerbeke (Bob B. & Joe J.) advise a 30 micron primary if the fuel lines are longer than 10' and a 10 micron primary if the filter is less than 10' away. They suggest not to use a 2 micron..... I replace far more lift pumps on boats with 2 micron filtration that I do on boats with 10 or 30's....

These engines really don't need 2 micron filtration, not even Racor advises it for this type of engine....

As an example our club launches (2 Westerbeke & 1 Yanmar) which run almost constantly from 7:00 am to 9:00 PM 7 days per week for almost 6 months per year run 30 micron primaries plus the standard on-engine filter. Two of these engines have now exceeded 10k hours.

I think your money would be far better spent buying a single Racor 500 with either a 10 or 30 in it, vs. two Racor spin on's.....

If you had an on-board fuel polishing system, with a  pump designed to handle 2 micron, than filtering the tank down to 2 micron is a perfectly fine practice. I won't personally install a 2 micron filter on the engine filtering system of our boat even though our tank is 100% polished.

P.S. The primary filters Yanmar re-labels & sells for their marine aux engines, (re-labeled Racor's), are 30 micron....

My engine continued to lose rpm and power over a period of 8 hours.  Seemed like a fuel filter plugging issue.  After some review I changed both the racor and engine filter.  The racor filter ends are steel and had badly rusted.  The filter was plugged with rust from the filter.  the filter was the cause of the problem.  I have never seen water in the glass bowl.  I am considering removing the racor unit
n

That is interesting that a filter would rust in a none-moisture environment. Plastic construction may be best.

My engine mounted filter rusted through! Looked new and I never saw water in the bottom of Racor.