----- Original Message -----
From: "ronald barr" rwhb@email.msn.com

Hi Ron,

Several possibilities come to mind:

1. A Racor 900 is undersized for your engine. That seems unlikely but DD's
   do move a lot of fuel relative to what they actually burn

2. There was some sort of missed communication between you and the guy you
   talked to at Detroit;

2a. He thinks that you're using the two filters in series and said that the
first one should be 30 micron (with the second one at 2 micron).

2b. You called your Racor a "primary filter" and he gave you a nominal
rating for an engine mounted primary fuel filter. I've discussed the
potential for this sort of thing in previous posts.

3. The 30 micron recommendation is the company line and is intended to
   generate sales of their own engine mounted filters. This also seems
   unlikely.

4. Your contact at Detroit simply isn't familiar with this type of filter
   installation.

Using a 30 micron element won't actually hurt anything. It just makes more
work for the filters downstream from it. Technically that means you're
needing to change your engine mounted filters more often than if you used 2
micron Racor elements but in practice you probably are changing those
filters sooner than you need to anyway.

BTW: Changing filters prematurely is FAR better than having one clog and
kill your engine.

Suppositionally yours,

Alex

Gotta jump in here, as I've now got three different angles on filter size for
primaries, and they're all valid sort of.

First off, about the 30 micron filters, I can confirm that the Detroit Diesel
service manual for my 671s specifies 30 micron filters for the primaries, so
that ain't just hearsay from a misinformed rep.  That's writesay from the whole
company, right or wrong.  I didn't read the whole message from which Alex was
snipping, so I don't know which Detroits Ronald has, and subsequently don't
know whether this info is applicable, but a Detroit's a Detroit..

I exchanged private emails with Bob Austin recently.  Part of the message
related the tale of a friend of mine delivering an old wooden 65-footer up the
coast of California, facing not atypical stuff at Pt. Conception (meaning
choppy 20-footers).  He rounded Pt Conception in the engine room, changing out
2-micron primaries from his two sets of dual-primary Racors over and over.  Had
a cases of 'em on board. He swears he'd never do that again, and that he's got
30-micron filters in those primaries now.  I forgot to ask him at the time
about his plan for keeping the little stuff out of his secondaries

Hoping Bob doesn't mind me citing him, but he also thought 2-microns was too
fine for the primaries, and he ran 10s in his.  But he also said that he had a
third filter, a pre-primary, with 30s in them that he switched in whenever he
went offshore, which struck me as a pretty good idea.  He also said he polished
his fuel before any offshore trip, another very sensible thing to do that I'd
bet a lot of us skip.  Alex, you don't have to bother, do you, because you've
got an onboard fulltime polishing system, no?

It seems that having 2-micron filters in your primaries WOULD be a good idea if
you could make sure that they weren't the first line of defense against the big
crud.  Ideally, you'd have a full-time autopolisher at the tanks and, in
series, a switchable pair of 30s, followed by a switchable pair of 10s,
followed by a switchable pair of 2s, followed by a secondary with a 2-micron
filter that you'd never have to change (just the simple act of changing the
secondary offers the chance to introduce impurities if the procedure's not
perfect (think pitching and seasick on the high seas with dirty hands and your
O-ring and cover just slipped under your floorboards)) .  Sounds OTT, but if
somebody handed me a boat with all of the above, I don't think I'd change it
out.  That is, if all that filtering didn't impede the flow to the engine.
Hmmm... I wonder where I'd mount all that stuff on Bomar.

Doug Hoople
M/V Bomar
1963 Stephens Bros. 50 FDMY
Sausalito, CA

Alex Hirsekorn wrote:

At 02:04 AM 7/6/01 +0100, you wrote:

Doug,
I have to jump into this again.
The secondary filters on most engines are fairly expensive and often only
available from a factory source.

If you don't use 2 micron stuff in the primaries, then you will be changing
the secondaries out instead of the primaries. Take your choice. But between
the cost of the secondaries and the hassle of changing secondaries
(repriming, etc.) and the need to stop the engine to change the
secondaries, why would anyone want to use 10 or 30 micron stuff in the
primaries which are cheaper, readily available and if you have a double
filter setup, can be changed without stopping the engine?

My 40 years experience with this problem has led me to this conclusion. In
otherwords, I used to have the same ideas that are being expressed here on
the forum. But that was before I knew better.
Regards,
Mike

Capt. Mike Maurice
Near Portland Oregon.

At 02:04 AM 7/6/01 +0100, you wrote:

I didn't have time in the previous email to address the fuel tank problem
mentioned, so here goes.

Anyone who is changing out filters like the crazy, hasn't got a filter problem.
They have a contaminated fuel tank problem. There should be not confusion
between the two types of problem. Badly contaminated fuel tanks, are
usually due to poor or absolute lack of maintenence. Where does the idea
come from that fuel tanks don't require periodic clean outs?
This sort of confusion is a mark of the rank amateur. There are only 2
things a diesel needs to run. Clean air and clean fuel. No amount of
filters will solve badly contaminated tanks. After all, what are you going
to do when the main fuel line is plugged, before the filters?

Kindest regards,
Mike

Capt. Mike Maurice
Near Portland Oregon.

Hi Doug,

I think that a couple of your points here need a bit of clarification.

----- Original Message -----
From: "Doug Hoople" doughoople@earthlink.net

Diesel

This may seem, at first, to be just semantics but Racor or other aftermarket
filters are NOT primary fuel filters in the lexicon of engine builders or
filter manufacturers. They would be better described as "auxiliary" filters
or simply by brand and part number. This topic came up last April and the
following links will take you to some of my posts on the subject.

http://www.samurai.com/lists/trawler-world-old/2001/04/0464.html
http://www.samurai.com/lists/trawler-world-old/2001/04/0553.html
http://www.samurai.com/lists/trawler-world-old/2001/04/0919.html

Actually no. My boat has twin gas engines and will empty the tanks in 8
hours or less (not really a trawler I guess) so polishing would be
unnecessary for me. My advocacy of polishing systems is based on logic and
almost 30 years in the petroleum and filter business. For more information
on why I think an onboard polishing system is a cost effective and generally
good thing you could check the following links.

http://www.samurai.com/lists/trawler-world-old/1999/09/0038.html
http://www.samurai.com/lists/trawler-world-old/1999/11/0445.html
http://www.samurai.com/lists/trawler-world-old/1999/11/0523.html
http://www.samurai.com/lists/trawler-world-old/2000/10/0455.html

BTW: I just read Mike Maurice's posts on this thread and I agree
wholeheartedly. If you're going to clog a filter then you want it to be the
easiest one to fix (IOW: the Racor). If you're going to be replacing
elements prophylactically you want them to be the cheapest and most easily
available (IOW: usually the Racor). Finally, what Mike refers to as "Tank
Maintenance" and the onboard fuel polishing that I talk about, while not
absolutely identical, are pretty darn close to being the same thing.

URLly yours,

Alex

At 02:14 PM 7/6/01 -0400, you wrote:

David,
I have been thinking some more about this. It seems to me that the issue is
VERY subtle.
Does the use of small micron filters at the primary stage cause more
potential damage from overheating of injector(low fuel flow).
Versus, large micron filtration in the primary stage and the possible low
flow of fuel caused by the secondaries clogging up.
After all, what we have here in simple terms, is secondaries that clog and
can't be replaced as easily as primaries, versus primaries that catch
almost everything and are replaced frequently.
The validity of the Detroit Recommendation is in question, partly because
we don't have an explanation of their thinking. I will see what I can find out.

Capt. Mike Maurice
Near Portland Oregon.

problem.

The older two cycle Detroit Diesels use the fuel for two things, to burn
and to cool the injectors. This is why they pump around so much fuel and
why GM wants to maintain this flow. Also, they do not use a supper high
pressure injector pump, but instead fill the injector at low pressure and
whack the injector with a cam to make it squirt. They are naturally
aspirated, but they use a blower to scavange the cyclinders at the bottom
of the compression stroke.

The point of all this is that these engines are very very different than
the four stroke Cats, Fords and such.

I'm not an expert, obviously, but I have 10 years of ownership with these
boys and the mechanics do not want low fuel flow and hot injectors. Ron
Barr's diesel experts are giving him the straight skinny, 30 micron. Now,
how much tolerance to dirt particles (less or More) the GM injectors can
stand I don't know. They represent the largest number of diesels ever made
by a huge factor. They have billions of hours of knowledge and of course,
they know they need clean fuel and air. I would hesitate to recommend
drastic changes to this specification without very careful study, at least
as far as the GM 2 cycles are concerned.

Skooch Hatteras 42 LRC - twin 4-53n
4 cylinder, 53 cubic inches per cylinder, 2 cycle
Detroit Diesel 116 horses in marine configuration

David Stahl

Kennett Internet Services, 112 S. Union Street, Kennett Square, PA 19348
610-444-9008              Visit our web site at http://www.kennett.net

At 06:02 PM 7/6/01 -0400, you wrote:

I called Pacific Detroit Diesel and talked to Dave. Here is what he says.
The detroits used in the Coast Guard boats with 6-92's have 12 micron
secondaries on the engines and they use a double racor's with a valve for
the primaries. The primaries are 30 micron.
That implies that if you used 10 micron in the primaries on detroits you
would not need to goto 2 micron, because the secondaries are 12.

Point taken. There would seem to be little to gain by using smaller micron
filters for the primaries than for the secondaries.

This may not apply to all Detroits. But it does the elevate the discussion
to a new plateau.
Regards,
Mike

Capt. Mike Maurice
Near Portland Oregon.

Michael,

I think you'll find a lot of powerboaters, some of them VERY experienced, who ain't
got that oldtime clean-fuel religion, although I'd wager you'd find a lot fewer of
them among the oceangoers.  There are many boaters who go for years without a clue
about what's going on in their fuel tanks and have no idea how virulent the
activity is in them.  Among sailors, it's a whole lot worse.  I've read any number
of stories of sailing auxiliary diesels failing in the rough stuff from clogged
fuel lines.

I agree that you need to exert yourself to the max to clean your fuel, a point
that's been brought home nicely on this list.

BTW, the guy who did the delivery was no rank amateur.  He's a very capable,
experienced yachtsman, with plenty of ocean miles under his transom.  It wasn't his
boat.  It was a delivery, and he was on as crew (the skipper was up driving, no
fool).  I've not done any deliveries, but I suspect that your timing and options
are not as robust as they'd be if you were driving your own boat.  Do delivery
captains normally head straight for the fuel tanks, pull 'em apart, and start
polishing the fuel?  I'd rate that as a relatively rare occurrence were I given the
option of a wager.  I agree, though, that my friend's solution of 30s in the
primaries with no other line of defense may be less than ideal.

Doug Hoople
M/V Bomar
1963 Stephens Bros. 50 FDMY
Sausalito, CA

Michael Maurice wrote:

I have a old 43' Viking with twin 6-71N Detroit Diesels. I use a Racor
1000FG filter for each engine and they both have vacuum gauges. I only use
the brown (2 micron) filter elements. In 1998 I cruised for a year. I
traveled north up the Hudson to the Erie Canal, across to  Lake Ontario and
then up the Rideau and then down to Montreal. Then up backtracked to the
Thousand Islands and then went to Sorel and down through Lake Champlain
back to the Chesapeake. Then after a month or two we took off for Florida
and then did the Bahamas for 9 weeks and then back home. The total fuel
consumption for the whole deal was 7000 gallons which I know is awful by
trawler standards but cheaper than a new boat.

The point of all this is that we used one set of brown 2 micron filter
elements for the whole trip. The vacuum gauges never went up so I did not
change the elements. I was paranoid about the bad fuel stories and I had a
huge pile of different color Racor elements on board. There were no
injector problems or any other engine problems.

I doubt that 2 micron Racors were even considered when the books were
written for my old Detroits. My normal filter vacuum is between 0 and 1" of
vacuum so there are no flow problems with the 2 microns.  Once with a
clogged filter I saw the reading go all the way to 18" but the engines were
running fine. I cannot imagine any reason to not use 2 micron (unless they
come out with a 1 micron).

Frank Burrows 1979 43' Viking MY  Piney Narrows Marina  Chesapeake Bay