Guest 000 Posted October 27, 2014 Share Posted October 27, 2014 Why is nothing ever easy? Now I have a question about fuel filtration. The engine on board is a Perkins Perama M30. The fuel comes out of the tank, through a water trap, then to an engine mounted Perkins branded filter and then to the high pressure fuel pump. I am thinking that after the water trap I should have two fuel filters. Amongst my box of bits I have a new CAV filter assembly fitted with a CAV 291 filter so I could put it into the fuel system, but, I am altogether unable to find out the micron rating of both the Perkins and the CAV filters. It seems to be a big secret! I imagine it is no use having two filters of the same micron rating - the first is going to catch all the gunk and the second, nothing. I think that the ideal setup would be to have the filter closest to the tank at, say 10 microns and the next at 5 microns for maximum filtration benefit. Is this how it works? And where do you find the micron rating for fuel filters? Thanks Link to post Share on other sites
erice 732 Posted October 27, 2014 Share Posted October 27, 2014 rather than install a 2nd set of filters why not shorten your engine filter replacement cycle? a whole lot cheaper and easier for similar results Link to post Share on other sites
Guest 000 Posted October 27, 2014 Share Posted October 27, 2014 Well yes, that makes a lot of sense to me. I've had just a single filter on the engine since I've owned the boat (4 years), with a six monthly filter replacement. No problems. Its just that I get a lot of 'What? You only have one filter??' So I assume I'm doing it wrong with my single filter. Link to post Share on other sites
wheels 543 Posted October 27, 2014 Share Posted October 27, 2014 The CAV filter units are a great little unit. Although they are pretty much all Chinese copies now. You won't get anything better for the price. The filter elements themselves are 5 micron and ideal for the final filtration micron size for an engine. The downside is that they use gravity only, to filter out water. That is where the more expensive filters come in. Racor "spin" the fuel as the fuel runs through the Filter body and works better at separating the Fuel/Water. Some models can even have probes to signal an alarm to let you know water is present in the Bowl. But these units are scary stupid expensive. Racor are the Rolls Royce of Filtration, but the price is stupid. I think there entry level unit for an engine your size is like $300 to $400 range. The idea of changing the filter more often is not the way to think about it. It is about particle size rather than quantity of particles it has to deal with. Twin filters is not about dealing with more dirt/water, but that the filters are not the best at taking the dirt/water out and hence the second filter to be a second trap. In larger installs, you have a Secondary filter, which is 10micron that removes the larger particle size and water and that unit is first in line from tank. Secondary means the second away from the engine, secondary as in a larger micron size or Second as in not the main filtration size. The primary, or main filter that is the final filter before pump, needs to be 5micron or better. Link to post Share on other sites
erice 732 Posted October 27, 2014 Share Posted October 27, 2014 all makes sense which means you need to know the microns if you diy the install Link to post Share on other sites
waikiore 410 Posted October 27, 2014 Share Posted October 27, 2014 Racor 10 micron complete set up $195.00 at Whitings, for up to 70 hp, Eric is the man to talk to. Link to post Share on other sites
Guest 000 Posted October 27, 2014 Share Posted October 27, 2014 Wheels, thank you for your reply (and to all my other posts). I knew this filter business was going to be complicated...... I havs discovered that the primary engine mounted Perkins branded filter recommended for the engine is 25 microns - seems big to me. If I use my CAV unit with its 5 micron filter as the secondary unit then the primary unit would not be doing anything, is this correct, and can I live with this setup? Alternatively, I could re-run the fuel lines so that the engine mounted filter is the secondary and the CAV becomes the primary. Then the watertrap would be on the primary - would this be a problem? Link to post Share on other sites
wheels 543 Posted October 27, 2014 Share Posted October 27, 2014 Not sure what the 25micron would be. Perkins used to always run with the CAV filters and often mounted on the engine and as a dual unit on larger Engines. 25 is going to take large particulates out, but it most certainly needs to be the first filter in the line from the Tank(secondary). The Racor waikioie suggest is a very basic screw on cartridge and the replacement cartridges are not the cheapest. Nothing wrong with it, typical top quality of Racor pedegree. Just no see through Bowl, so no idea if there is water to worry about. Their next unit up about $109. It takes a filter that goes between a top and bottom unit, but twice as long as the CAV filter cartridge. The beauty of the CAV is that many manufacturers make the filter cartridge and they are usually under $10 each and available from almost anyone. I normally buy a box of 10 at a time, so I have spares should I need. Never have of course, most likely because I have the spares. Link to post Share on other sites
Guest 000 Posted October 28, 2014 Share Posted October 28, 2014 OK, this is what I got from a very helpful man at Transdiesel. The Perkins M30 is built on an engine supplied by Ishikawajima Shabaura Machinery Ltd. ISM build basic, no frills naturally aspirated engines primarily for the agricultural sector and are designed to operate in remote areas where servicing is uncertain and on fuel stored in a cow trough and fed to it by a shovel. Well, no, he didn't actually say that but did say that engine tolerances were such that it would happily chug away on less than pristine fuel. He also confirmed that the 25 micron filter he sold me earlier is the correct one for the engine. The workshop manager then joined the conversation and said that multi filter installations were really for larger engines with correspondingly larger fuel tanks where the fuel\water interface was greater, thereby causing...... By now my eyes were glazing over, but suffice to say that considering I only had a 30 litre tank I only needed the one filter and water trap if I practiced normal fuel hygiene. So I think that I will install the CAV filter unit as a secondary filter anyway, mainly because the water trap on it looks a lot better than the glorified jam jar I currently have. The only question remaining is, if I install an extra filter does this increase the workload on the fuel lift pump? Link to post Share on other sites
wheels 543 Posted October 28, 2014 Share Posted October 28, 2014 remote areas where servicing is uncertain and on fuel stored in a cow trough and fed to it by a shovel. Yep seen a few Boats with Fuel systems like that. No worries for the lift pump. The fuel that engine sucks is really low compared to the Volume the filter is capable of passing through. Link to post Share on other sites
erice 732 Posted October 28, 2014 Share Posted October 28, 2014 primary diesel filtration (from the 30ltr? tank) on my small 16hp engine is handled by the glass bowled water separator/filter http://www.volvopentashop.com/Volspec/e ... 31%2F16139 nz$345 for the racor system http://www.trademe.co.nz/motors/boats-m ... 503457.htm Link to post Share on other sites
waikiore 410 Posted October 28, 2014 Share Posted October 28, 2014 Hi Wheels, Not a screw on cartridge and yes does have a sight bowl underneath, slightly smaller than the standard CAV/ Lucas/Delphi 296 type. Link to post Share on other sites
Chewing Gum 17 Posted October 29, 2014 Share Posted October 29, 2014 I like the racor type, had a CAV and threw it away as they are very messy to change. There seems to be more diesel bug around these days for example the rubbish Orams were selling for a while there so a good filter setup is a good plan to prevent your engine stopping in an emergency situation. Link to post Share on other sites
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