What setup do you have now? T the fuel supply line with a shut off on the inlet and outlet of each racor would be the easiest. Or, exchange what you've got for the dual racor assemblies. I prefer to run 10 micron racors, and while it's not ideal, I can shut one engine down and swap a racor and get restarted in about 60 seconds.
I have the dual racor set up. you flip a valve if you have a filter problem. its a great set up and could be a real life saver in the wrong conditions and wrong location.
Dual racors are idea but if you already have singles then just add an extra one with Valves as CaptJ suggested.
The later dual Racors with a single lever control is very cool. I still have the older dual design with 4 valves. Racor and the residual sales company does not offer an upgrade to the single valve system. If anybody has salvaged a set of the newer valves and plumbing from a dual 500 or 1000 filter set and for sale cheap, please let me know. Lots of stuff to possibly trade back.
As needed. Watch your low pressure (vacuum) gauges. When a lot of water collects is when my filters get replaced also. Don't let the fuel dye confuse you. A little dust or dirt on the filters just make them filter finer. Again, your gauges will tell you when to replace.
This, when I deliver a new (to me) boat, I first pull them up and inspect before even leaving the dock, then I check at the end of each day for the first couple of days and change if they're black. If they stay clean, I'll check every other day. If there is a vaccuum gauge that records vaccuum I will inspect that right off the bat for a baseline and just watch it a few times each day at cruise speed. Run 10 microns, with the newer lower sulpher diesel, I've had 3 new or almost new yachts where the secondaries got plugged to where the motors were alarming low fuel pressure and the 30 micron racors looked almost new...........I'd much prefer to spend 60 seconds changing racors, than 60 minutes and needing a fuel jug to change secondaries.
Yeah I don't have the vacuum gauges, and I ordered a case of 20-20-30 Racors on the advice of my engine surveyor
Remind us; what engines do you have and what secondary filters are in use? Do you think you have a dirty fuel issue?
I have freshly rebuilt 6v92's that run great, about 200 hours. Not sure what secondary filters I have I'll have to look. Just trying to get up to speed on doing most of the work myself because that's how I am. And I like the dual set up that skip miller was mentioning
I go by the gangue, mine also have a water sensor alarm. I do visually inspect every time I go through my pre flight check list.
Detroit's used a couple of different secondary assembly's. Hopefully you have the big spin on filters (not the cartridge PIA's). I have DDC & Donaldson part numbers on a list with their filtration numbers in mic if you need them. Give me the part number of what you have in place now, that way I can double check your pipe size (neck that screws into the filter) and offer correct filter numbers. You may learn that Donaldson offers a great filter a little cheaper. My Detroit shop sells both brands.