On Nov 11, 1:23*pm, "Roger Long" wrote:
I drained my primary Racor filter today and have this to report on one of
the world's smallest on board fuel polishing systems:

There was not a drop of water or speck of dirt in the drained fuel. *It
looked perfect. *The 2 Mu filter element was slightly discolored but with
nothing visible on the surface and it was clearly not challenged by anything
in the fuel.

The previously white polishing system filter was a dark grey brown and had
clearly picked up quite a bit of stuff. *No visible loading though.

This system:

http://home.roadrunner.com/~rlma/StriderFuelSystem.htm

exceeded all expectations in operation this season. *It's simple and
intuitive to operate, works in almost any mode, and was trouble free. *The
only change made during the season was to add a high point loop to the
common vent so fuel wouldn't flow into the lower tank at large heel angles.
The only operation challenge was forgetting to open the main tank valve a
few times since I close the tank which can siphon in case of a fuel leak.
Fortunately, the fuel pump makes a distinctive clattering when drawing
against a closed valve for several minutes before the engine starts to
stumble and I can open the valve from the cockpit.

The only surprise was the that transfer pump would only suck about 80% of
the fuel out of the lower tank when transferring to the upper tank. *Once
the boat was hauled, I determined that it is simply because the flow
capacity is so high that it sucks air down through the fuel. *With the lower
draw of the regular fuel pump, it will draw down to a lower level. *The
operational quirk then is that the polishing system needs to be off to use
the last of the fuel in the keel tank. *This would be a rare occurrence
though since drawing from a tank that low runs the risk of drawing air into
the system due to sloshing.

This whole system is a testament to the value of a group like this, even for
a boat designer. *Thanks to all who took time to discuss it while I was
developing it.

--
Roger Long

In order for "the gumk" to grow in your fuel tank their must be water
present, no water, no gunk. This is the main reason it is always
reccomended that you keep your tank full. A full tank will not draw
moist air into the tank through the vent as the fuel expands and
contracts when it warms and cools.If you've got water in the fuel,
your going to have some kind of growth unless you treat your fuel with
an aditive like Biobor. Filtering it, or as some prefer to call it,
polishing it, will remove the growth, but it may not remove the water,
depending on how long your fuel pickup is. Your best bet is to treat
your fuel on a regular basis, keep the tanks full at all times, and
change filters at the first sign of trouble. Polishing is only going
to make the problem go away for some period of time, but it will be
back.

Another point, those 2 micron filters on your Racor, check with your
engine manufacturer, I've never heard of one reccomending more than a
30 micron filter as the promary. Using more restrictive filters can
cause problems with your supply pump, or, even worse, cause the engine
to run lean. That will cause the engine to run hot and, over the long
run, cause all kinds of other problems.