Brian, as a high volume user of JD engines, I'm sure you're aware of JD's position that anything more restrictive than a 30 micron primary filter is not recommended. In fact, JD doesn't even appear to support Racors at all. When my JD 6068 experienced fuel pressure problems, JD made the local JD service technician by-pass the Racor to make sure that wasn't the problem. In the past I was a supporter of 2 micron primaries and to just change the secondary engine mounted filter annually. After all the Racor cartridges were much expensive than the $35 Yanmar filters and a whole lot easier to change in any condition. And a vacumn gauge and visual inspection will give me forwarning of primary filter problems when there isn't an equivalent forwarning for secondary filters. Now I've reconsidered, but done so without factual evidence yet to support my current thought process. I now use 10m primaries and am considering JD's recommendation to use 30m primaries. My new thought process is based on my assumption that the amount of trash in the 3 to 10 or even 3 to 30 micron range is probably insignificant. If this assumption is true, the amount of sub 10 or 30 micron junk that gets by the 10 or 30 micron primary will not be so much that the secondary filter will ever require changing more often than recommended by the manufacturer. Obviously, well at least I think it's obvious, that a 10 or 30 micron primary filter will not clog as soon as a 2 micron primary filter. Although I don't have engineering evidence to support my new thought process I do have some practical experience. My new boat's first load of fuel was bad. It would clog, or nearly clog, a 2 micron primary filter in less than 20 hours. So I changed to a 10 micron primary. Doing so doubled the amount of time it took to clog the primary. After changing primaries 3 times (twice they where 10 micron units) I changed the secondary 2 micron JD filter and it appeared clean. I did have the tanks professionally cleaned at that point, so I can't effectively do a similar test with 30 micron filters. As someone else pointed out, this topic and the twin vs single engine topic are like comparing dogs and cats. Well, maybe not, dogs are better pets than cats--aren't they :-) Gil "Dog's Life" OA Classico 50 Hi Gil Yeah I think dogs are much better pets as I sit here in my office my 100lb 13 year old rotwelier lays under the desk he's been coming to work with me every day for 13 years. But I can see the logic of a cat if my buddy was 5lbs he would still be able to go cruising with the family at 100lbs he's gotten to old to handle it. I can also see the logic on both sides of the twin vrs single argument but I'm not seeing the logic in this argument. I have received an awful lot of off line responses and almost everyone in the 10 micron camp says the same thing "this is what the manufacturer recommends". But nobody including the manufactures can tell them why. Now they do give some reasons like flow rate and that's not accurate. They caution about exceeding the change intervals on the secondary and that's not (or shouldn't be part of the 2 micron philosophy). And then they go into a lot of gook about how a filter is not a point of failure and how we are all to stupid to read vacuum gauges. I think Frank's post best explains why they have this position. The Idea of a 2 micron primary is not as new as some may think. It gained popularity when Passagemaker magazine began talking about but the idea was around before Passagemaker even existed. It came to my attention about 15 years ago and we have used it on our boats for about that long. We primarily build production boats so the first of any model has to be inspected and approved by the engine manufacturer to insure warranty. Detroit, CAT, Cummins and John Deere have all given us approval on 2 micron primaries the reason we get approval is because it meets the spec they call for. The primary filter has to have at least the minimum required flow rate and the element has to be of a micron rating at or below the manufactures spec. So it can be lower or finer but it cannot be higher or courser and the flow rate has to be adequate with the element installed and there's more but nothing relevant to this discussion. Now if you or I as a boat owner call the dealer and ask them about it we will likely get the easy answer or company line "just do what we tell you or something terrible will happen" and again just take a look at franks post I think he explains why very well. As a builder we don't get treated that way. We get one or more application engineers that come here and perform all there tests look at all the drawings and make sure everything meets the spec. These guy are usually quite willing to address a different idea and I have never had any trouble with the 2 micron primary and never thought I would because it meet the spec. It has been suggested in some posts that you will void your warranty if you use a 2 micron primary and that's just plain wrong. If you used a 30 when the spec says 10 or you exceed the recommended change interval on the secondary to the point where it deteriorated and contaminated the injection system then sure you may very well have warranty problems. But if your flow rate is within spec the 2 micron element will not effect your warranty at all. In your situation I'm not sure going to a higher micron rating is a good idea You primary is going to trap whatever it rated for anything finer will be trapped in the secondary or pass thru the injection system. So a higher the rating on the primary will cause more to be trapped in the secondary. If your clogging the 2 micron primary I would increase filter area or pipe a second filter in parallel. I have gotten replies from some who say they would like to use the 2 micron primary but it plugs up very quickly. I my view heres the bottom line there is no free lunch if there's dirt in your fuel you want it to end up in the filter. In the traditional system some of it is going to end up in the primary and some will end up in the secondary. You can't choose what micron level of crap is getting into or developing in your tank you can use a vacuum gauge but you will only be getting half the picture you have no way of knowing the condition of your secondary. You have allowed the crap to get closer to the injection pump and only one element is keeping it from entering the injection system. Even with good maintenance you still may end up in a situation where you don't know which filter has caused you to shut down or you didn't get warned before a shut down. You may end up having to change a secondary on a hot engine and it is probably more difficult and definitely more critical than the primary. The 2 micron secondary solves all these problems if it's plugging up quickly add filter area better to trap it there than in the secondary. The only situation I can see that this might not work out well on would be some smaller engines with diaphragm pumps. I have gotten some posts that suggest some cannot tolerate much vacuum at all. That could be the design and arrangement of the tanks and lines or a pump that is just very small with a very low flow rate. In that case you may have no choice other than the traditional system typically small diaphragm pumps will better tolerate pressure (on the secondary side) than they will tolerate vacuum (on the primary side). That's enough of this time to go cruising. Brian Palmetto FL

> ...I can also see the logic on both sides of the twin > vrs single argument but I'm not seeing the logic in this > argument. You asked for a logical response to the "other side" about a week ago. I agree with you - most of the responses have been along the lines of recommendations from others. Some of the recommendations have been exceptional ones. I trust and follow the ones from my engine manufacturer, even if I don't always see the brilliance of them immediately. Still, you didn't receive a logical answer. I'll give you one. You might not agree with it or you might feel that your logical analysis is more correct. Still, logic is logic. Here goes... On my boat, I like the operational components to be used and operational. I close every seacock on the boat when I leave it. We have two showers and two heads and my wife and I make sure to use both of them even though it means cleaning twice as much. I have two sets of house battery chargers - I use both, switching off every few uses. I feel that an unused item is an item that will fail when it is needed for use. This same logic can extend itself to fuel filters. If I have a 2 micron primary and a 2 micron secondary, the reality is that the primary is doing all of the work. The secondary probably isn't adding much. In short, it really isn't being used. This violates the aCappella rule of logic - operational components should be used and operational. If I have a 30 micron primary and a 2 micron secondary, each filter is doing its part to clean the fuel. There isn't any extra work demanded on one over the other. I also change my filters at regular intervals and view and record the primary vacuum reading every 2 hours while underway. I have a pretty good idea when my filters are getting used up. The fact that JD suggests a 30/2 configuration is just icing on the cake for me. The bottom line is that it makes sense to me. ================ Jeffrey Siegel M/V aCappella DeFever 53PH W1ACA/WDB4350 Castine, Maine