> Somewhere there must be a > manufacturers rationale and test > results that support the staged > filter method and that it is not > based on old stationary engine history We already know a 2-micron filter will clog a lot faster than a 10-micron filter - ask anyone on this list who runs 2-micron primaries for validation - chances are, they've had to change their primaries while underway. Question is: is there benefit to running 2/2 filtration (2-micron primary, 2-micron secondary) over 10/2 (so-called stepped filtration, the industry standard)? I'll pose this question to the 2/2 folks: the fear is having the eingine-mounted filter clog underway and then have to replace, prime, and re-start the engine (the "Oh my gawd" factor). But is there any first-hand, real-life experience to back this up? I mean, is there actually gunk that gets past a 10-micron primary and clogs a 2-micron secondary between service intervals? Personally, I've never had it happen, but concede it's possible so the question becomes does that risk outweigh 1) vastly increased liklihood of 2/2 clogging (monitoring is, after all, a manual process and glass bowls eventually get foggy); 2) risk of possible engine damage due to elevated vacuum and fuel temps; and finally 3) the remarkably consistent guidance of billions of dollars of R&D and warranty dollars? But the 2/2 position seems so, well, logical - where's the flaw? I suspect the answer lies in the microscopic nature of the particles. We are worried about the stuff we can see (fuel tank gunk - rust, dirt, water, asphaltines, etc). The engine manufacturers are worried about microscopic-sized particles. At that level, they're okay with 10/2 filtration (in fact, they recommend it). Sure, a 2-micron filter will filter out the big crud, but unless the filter is very large, it will load-up and clog, placing a burden on the engine (their concern) and potentially cause the engine to starve/die mid-ocean (my concern). According to the experts (and my personal experience), using a properly maintained 10/2 system will not cause the 2-micron secondary to clog and an unexpected engine stop, but using a 2/2 system may. So, I think I've laid out the 10/2 position pretty well, albeit belabored (its not a simple position). I'll look for the 2/2 folks to move past logic and post their actual experiences with clogged 2-micron secondaries when installed in a 10/2 system. Depending upon that outcome (as I said, I've never had it happen), I'll have to weigh that evidence with the liklihood of having a 2-micron primary clog in a 2/2 system. I think that's the heart of the decision, at least for me. Peter www.SeaSkills.com