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Old 09-11-2006, 19:35   #31
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Here's what Raycor has to say about filter micron ratings:

Quote Racor makes filters with various filtration
efficiencies, but its standards for non-OEM (Original
Equipment Manufacturer) are 2, 10, and 30 micron
filter elements. The actual efficiency ratings for these
are 98%, 95%, and 90% respectively. Racor also makes
use of a 7 and 20 micron filter medium which are used
to meet certain engine manufacturer’s requirements
for a final filter and a primary filter.

Racor’s 2 micron filter medium should only be used
in final or secondary filters where the fuel is first
filtered by a primary filter. The primary filter for a 2
micron final filter should use a 10 micron medium.
The exception in using a 2 micron filter in place of
a primary filter is to obtain high-efficiency water
separation, and is usually used in marine applications
where the fuel supply may be cleaner but also may
contain water more often.
If the installation can
allow the use of a filter large enough, then a 2 micron
filter can serve in a system as the only filter in that

New high pressure common rail fuel injection
systems require high efficiency in removal of small
particles. The requirement is 95% for 3 micron
particles. Racor fuel filters have a medium designed
for these applications. Replacement elements should
state, “For Use With Common Rail Fuel Injection
Systems.” Dirt levels in fuel also direct the level of
efficiency required. Since the filters removes a
percentage of dirt particles, it follows that when a
much greater amount of dirt is present in the fuel, a
greater number of particles will pass through the filter.
Diesel engines used in earth moving or agriculture
should use fuel filters that have higher efficiency than
those for over-the-road or marine.

The planning must also take into consideration
whether the filter is to be installed on the engine or
the chassis and whether on the vacuum or pressure side
of the system. Filter installations on the engine make
the filter subject to high frequency vibrations which
reduces the efficiency level, (as do spill port metering
injection pumps).

See Racor brochure #7550 for additional information. Unquote

SEEMS TO ME, the usual recommendation is for a 10 micron primary filter followed by a 2 micron secondary filter in two-filter setups.

Note that if the filter is mounted on the engine, the filter efficiency is diminished through vibration.

Note also the "pass through" or "blocking" efficiency of the various Raycor filters. The 30 micron filter traps 90% of sediment/particulate matter at least 30 microns in size....that means that 10% pass right on through the filter and reach the secondary filter.

Commercial applications may not be the most appropriate model for marine recreational use, due to a number of factors including economy. I'm perfectly willing to buy cases of filters (and do) and change them out at the first sign of a significant increase in vacuum....LONG before they block enough diesel fuel to starve the itsy-bitsy Perkins 4-108 which only needs 2-3 ounces per minute at cruising speed.

I've never had a problem with the 2 micron filters in a primary application. However, I recognize that someday, somewhere, some nasty stuff might shake loose from my tanks and be a potential problem. So, I think I'll start loading my filter manifold (two 500G Raycors, either one selectable on the fly) with one 2 micron and one 10 micron filter :-))


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Old 09-11-2006, 19:46   #32
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I am a fanatic when it comes to keeping the engine running reliably and would use a 2 micron filter if I felt that there was justification
Agree on all points.

versus the real problem of continuously fouling the damn things continuously and unnesessarily.
Agree again: Never fouled the damn things, and plan to stay that way...

That being said:

On previous boat I kept loosing the engine every time I tried to motor across the Salt River reef in St. Croix. (Not a good thing)

After a while I just put the sails back up and sailed in every time I returned home.
Took me a while to figure out the problem:
The pick-up tube in the tank had a small screen that "algaed over" and left the filters un-employed.
I removed the little screen and never had a problem since.

Uh, moral of the story?
Whatever works good for you, your conditions and your boat, stay with it...
Just don't come on the 'net and complain because ya did not listen to the advise ya asked for.....

Life is sexually transmitted
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Old 09-11-2006, 20:58   #33
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The first filter outa the tank

The main point to make is that what works reliably is to pass the fuel through a rough cleanable and viewable screen (several models available) then through a "real" commercial filter and then through another filter, which may be one of those small things that so many installers use, and then to the one on the engine.

If one desires to use a 10, 7, or 2 micron filter for the one after the "brute commercial" one, it will not matter much which it is for most diesel engines. O.K. maybe a common-rail engine requires a 2 micron filter, yet who wants to make an engine check sticking one's neck within 5 feet of a common-rail fuel injection engine using such high pressure lines that, if damaged, can kill you? Does anyone out there have such an engine on their pleasure boat? Interesting thought.

One more point is that it is prudent to install an in-line "pull-through" fuel pump with a local on/off switch to purge the fuel system of air when changing filters as well as to turn on in an emergency when a filter is fouling and you are trying to get across some bouncy bar to get in out of a storm. With the pump on you get a few more hours of run time that the engine fuel pump will not give you with a marginal filter. Later, at your convenience, you change the filter, unless you are negligent.
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Old 10-11-2006, 02:55   #34
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From "Good Old Boat" magazine:
"Fuel And Water Filters - Simple Insurance Policies" By Bill Sandifer

Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"

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