Correct size for primary filter for QSB

8943post

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I noticed when I took the old Racors out that they were 10 micron, I was under the impression that the primarys filter needs to be 2 microns for a QSB 480. Which size is correct?
 

8943post

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10Mic is what it should be! The secondary last chance on the engine is 2Mic. If you use 2 mic on the racor, it will clog up rather quickly catching all the small and large particles. If you are interested why, read intro and multistage section to get a better understanding: Marine Fuel Filtration - The Seaboard Way

Great article...It's good to learn that you DON'T prefill the secondary but rather let the engine lift-pump fill the secondary thru the primary first. didn't know that...Thanks!
 

BillD

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Thats what I thought Bill...2 microns seemed too small for a primary but needed for the secondary.

Some owners DO run 2 micron filters on their primary Racors and "get away with it". I suppose in that case the tank/s must be new and the fuel @ the pump nicely filtered.

The tank in my Blackfin before I "cleared" it up would clog a 10 mic Racor 900 in under 30 hours of running...black goo.

Now I run Seaboard Marine's double/double 20/10 mic and can run for 100s of hours with zero issues.
 

captainlarry84

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Correct 2" micon on the primary motor filter & 10 micron on the secondary Racor filter.

Yanmar is 10 micron on the primary & 30 on the secondary Racor.
 

MDI45

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10Mic is what it should be! The secondary last chance on the engine is 2Mic. If you use 2 mic on the racor, it will clog up rather quickly catching all the small and large particles. If you are interested why, read intro and multistage section to get a better understanding: Marine Fuel Filtration - The Seaboard Way
It's not only that the filter will clog quickly ...but the engine companys suggest using no smaller then 10 mic due to ..it puts to much strain on the fuel pump.....and you wouldn't like the cost of a new pump
 
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