Whether you put the aux electric fuel pump
between the tank and the filter - or - after the filter is dependent upon the make/model of the fuel filter
. Some Racors and others are rated for either suction or positive pressure. Others are strictly suction units which require the aux electric pump
between the filter and the engine.
- - The most practical filter system is two parallel filters with valves to isolate one filter or the other from the fuel flow system. That way when one filter clogs you can select the other fuel filter
and continue operation while you change the clogged fuel filter.
- - Depending upon the engine sometimes the process of changing the "final" fuel filter mounted on the engine is very difficult so having your auxillary (fuel filter(s) before the engine) loaded with the same micron filter as the "final" filter will save the hassle of changing the engine mounted filter for a considerable length of time.
- - Whether you have dual filters in series is open for discussion as having a 10 mic first filter then a 2 mic secondary filter (matches the engine mounted filter) probably does not do much good whereas having a "switch-over" parallel system facilitates being able to bring on line a fresh clean filter without have to stop the engine and change filters while underway in huge seas and winds or entering a complicated harbor at night.
- - You can purchase
dual "switch-over" parallel filter systems already assembled for a large amount of money
or just go down to the plumbing
store and build your own "switch-over" dual parallel system with some 3-way valves and tee's.