> I read your link and am curious to know > why you support it? My original thinking years ago was yours exactly: certainly, there must be 3-9 micron junk bypassing the 10 micron primary just waiting to clog the 2-micron secondary --- and then OH MY GAWD!!! - catastrophy will surely follow. But folks like Bob Senter convinced me that engine and filtration engineers carefully study this and design a total fuel filtration system, and not following those closely engineered guidelines disrupts the intent of the engineering. Just as the "2-micron is better than 10-micron" argument makes intuitive sense to some, following the guidance of millions of dollars in R&D makes sense to me, especially when they back-up their guidance with warranty dollars. Many people don't want to change the secondary filter for fear they will be unable to prime the fuel system and then OH MY GAWD!!! all over again. So they don't change the secondary at all. But the filter is a paper media, and eventually becomes waterlogged and starts to deteriorate - right into your injectors. My solution? learn to change your secondary, prime your fuel system, and follow the recommendations. > Do you believe that a vacuum gauge is > only useful at full throttle? Depends on the size of the engine (or fuel flow)relative to the size of the filters. When they start to clog, they clog very quickly - its not linear. So while I don't think they are useless at low flow conditions, I believe running the RPMs up will give you a better indication of whether the filters are clogging. > Do you believe that on -ngine secondary > filters are always easy to change? If a secondary filter cannot be easily changed, the boat has no place offshore. On single engine boats they are invariably easy to change. Like anything else, practice helps. > Have you ever considered that the very > act of changing the final filter could cause > sediment you don't see to get past it Sure, anything's possible. But, avoiding routine maintenance may cause the problem I noted above: what if the filter deteriorates? Where does that stuff go? You guessed right: into the injector pump/injectors. Look, everyone gets to live with their own decisions. If installing 2-micron primaries is a way to defer routine maintenance on the secondary filters, its asking for trouble. Until I see some real evidence (rather than supposition) that suggests there's a whole bunch of junk bypassing a properly maintained 10-micron primary and clogging a properly maintained 2-micron secondary, I'm going to follow the recommendations of engine and filter manufacturers - especially since it's their warranty money and R&D money on the line. I just don't think they'd be making these recommendations if it wasn't sound advice - they would stand to lose a lot and gain very little. Just my opinion - Peter www.SeaSkills.com