Changed my mind about fuel polishing
 

The sediment bowl on the Shelco filter I put in for my fuel polishing (or
Pre-filtering, whatever you want to call it) system doesn't drain
completely. I took it out of the boat today, poured off the fuel (Not a
drop of water BTW), and scraped out the stuff in the bottom:

http://home.maine.rr.com/rlma/Crud.jpg

Wow. I was saying a while ago that didn't think the system was necessary
for the cruising I do now. I would have agreed with anyone who said it was
a hobby affectation. I still wouldn't say "necessary" is quite the right
word but I sure am glad I have it just for tootling around in Maine.

This is the left overs from about 100 gallons of fuel purchased during the
year and isn't all off it since a gust of wind blew the plate over. About
half of the fuel was road diesel purchased at a high volume gas station.
Sure, the Racor could have dealt with this stuff and I could have dealt with
the Racor but, why? There was not a speck in the Racor bowl it looked just
like it did when I changed the filter and filled the sytem last spring.
Having this crud removed from the system in a way that makes having to deal
with it's disposal underway vanishingly unlikely is great.

--
Roger Long

Changed my mind about fuel polishing
 

"Roger Long" wrote in message
...
The sediment bowl on the Shelco filter I put in for my fuel polishing (or
Pre-filtering, whatever you want to call it) system doesn't drain
completely. I took it out of the boat today, poured off the fuel (Not a
drop of water BTW), and scraped out the stuff in the bottom:

http://home.maine.rr.com/rlma/Crud.jpg

Wow. I was saying a while ago that didn't think the system was necessary
for the cruising I do now. I would have agreed with anyone who said it
was a hobby affectation. I still wouldn't say "necessary" is quite the
right word but I sure am glad I have it just for tootling around in Maine.

This is the left overs from about 100 gallons of fuel purchased during the
year and isn't all off it since a gust of wind blew the plate over. About
half of the fuel was road diesel purchased at a high volume gas station.
Sure, the Racor could have dealt with this stuff and I could have dealt
with the Racor but, why? There was not a speck in the Racor bowl it
looked just like it did when I changed the filter and filled the sytem
last spring. Having this crud removed from the system in a way that makes
having to deal with it's disposal underway vanishingly unlikely is great.

--
Roger Long

I just attended a diesel seminar on Saturday put on by one of the local
yards. That black crud looks very similar to the bacteria that they showed
us. Is that what you have? You might want to look at it under a microscope.
If so, they recommend a biocide (any will do, mentioned was Biobor) and then
fuel polishing to remove the dead from the tank, since many tanks can't be
removed and cleaned easily. The fuel polishing issue seems to be important
to them for used boats that are recently purchased or ones with a continuing
problem vs. doing it on a regular basis for most boats.

According to the yard manager, who has about 30 years experience, one should
top off the tank as much and as often as possible as any condensation is
ultimately bad. He keeps a jerrycan with fuel in his lockbox, so that when
he returns and has only used a small amount, he can top it off.

FYI, all #2 is identical, at least per state. You want to ensure that your
diesel has the right cetane number, typically in the 48-51 range, and if
yours is like ours in California (41 - mandated by state law), then you can
get a stanadyne additive to bring it up. Apparently, many of the long haul
truckers fill up in Nevada before they cross the border, since Nevada serves
the good stuff.

He also recommeded a dual primary system if you sail offshore.

--
"j" ganz @@
www.sailnow.com

Changed my mind about fuel polishing
 

"Capt. JG" wrote

I just attended a diesel seminar on Saturday put on by one of the local
yards. That black crud looks very similar to the bacteria that they showed
us. Is that what you have? You might want to look at it under a
microscope. If so, they recommend a biocide (any will do, mentioned was
Biobor)

I use Star Tron which is an enzyme that causes any bacteria present to
detach from the tank walls and clump up so that it can be passed steadily to
the filters instead of going through all at once when stirred up in rough
water which is usually when you don't want to deal with a clogged filter.
It's a non-toxic alternative to biocide. I put it in with every batch of
fuel since each refueling can expose you to new bugs. I'm pretty sure it
works because I had a lot of stuff show up in the sediment bowl (pre
polishing system) right after I started using it.


According to the yard manager, who has about 30 years experience, one
should top off the tank as much and as often as possible as any
condensation is ultimately bad. He keeps a jerrycan with fuel in his
lockbox, so that when he returns and has only used a small amount, he can
top it off.

I see you missed the long thread on topping up tanks. Just because he did
it for 30 years doesn't mean it's necessary. Read the thread and come back.
Minimizing the surface area of fuel in contact with the air is a good thing
to do but it's a crazy obsession in the actual hassle/benifit analysis.


FYI, all #2 is identical, at least per state. You want to ensure that your
diesel has the right cetane number, typically in the 48-51 range, and if
yours is like ours in California (41 - mandated by state law), then you
can get a stanadyne additive to bring it up. Apparently, many of the long
haul truckers fill up in Nevada before they cross the border, since Nevada
serves the good stuff.

Now, this is interesting. I want to find out more although I expect Maine
isn't mandating weak fuel.


He also recommeded a dual primary system if you sail offshore.


That's essentially what I have although one of the filters is of higher
retention capacity and running separately all the time.

Another aspect of my system is that the fuel is being sucked from the tank
much, much, faster than the engine would draw (and this is especially an
issue on my Yanmar where the return line doesn't go to the tank). This
means that crud drifting around just below or near the pickup is
significantly more likely to be drawn in and recirculated through my big
Shelco filter.

--
Roger Long

Changed my mind about fuel polishing
 

"Roger Long" wrote in message
...
"Capt. JG" wrote

I just attended a diesel seminar on Saturday put on by one of the local
yards. That black crud looks very similar to the bacteria that they
showed us. Is that what you have? You might want to look at it under a
microscope. If so, they recommend a biocide (any will do, mentioned was
Biobor)

I use Star Tron which is an enzyme that causes any bacteria present to
detach from the tank walls and clump up so that it can be passed steadily
to the filters instead of going through all at once when stirred up in
rough water which is usually when you don't want to deal with a clogged
filter. It's a non-toxic alternative to biocide. I put it in with every
batch of fuel since each refueling can expose you to new bugs. I'm pretty
sure it works because I had a lot of stuff show up in the sediment bowl
(pre polishing system) right after I started using it.

Interesting... I'll check out Star Tron. Thanks.


According to the yard manager, who has about 30 years experience, one
should top off the tank as much and as often as possible as any
condensation is ultimately bad. He keeps a jerrycan with fuel in his
lockbox, so that when he returns and has only used a small amount, he can
top it off.

I see you missed the long thread on topping up tanks. Just because he did
it for 30 years doesn't mean it's necessary. Read the thread and come
back. Minimizing the surface area of fuel in contact with the air is a
good thing to do but it's a crazy obsession in the actual hassle/benifit
analysis.

No... didn't miss it. He's dealing with bio/water issues every day. I think
I'll trust his experience, although he didn't say to be obsessive about it.
He's advocating exactly that... minimizing the surface area. There's always
going to be water in the bottom of the tank. The bacteria eats the diesel
and lives at the line between the two. It's not just about condensation, as
there might be another avenue for water intrusion, such as a poor seal on
the filler cap. I don't think taking a couple of minutes to top off a tank
is obsessive. Seems like a good idea, especially keeping a jerrycan in the
box. It's a fairly long drive to get to a fuel dock for me.


FYI, all #2 is identical, at least per state. You want to ensure that
your diesel has the right cetane number, typically in the 48-51 range,
and if yours is like ours in California (41 - mandated by state law),
then you can get a stanadyne additive to bring it up. Apparently, many of
the long haul truckers fill up in Nevada before they cross the border,
since Nevada serves the good stuff.

Now, this is interesting. I want to find out more although I expect Maine
isn't mandating weak fuel.

I believe it's a low sulfur content issue, with the desire to lower air
pollution levels.


He also recommeded a dual primary system if you sail offshore.


That's essentially what I have although one of the filters is of higher
retention capacity and running separately all the time.

Another aspect of my system is that the fuel is being sucked from the tank
much, much, faster than the engine would draw (and this is especially an
issue on my Yanmar where the return line doesn't go to the tank). This
means that crud drifting around just below or near the pickup is
significantly more likely to be drawn in and recirculated through my big
Shelco filter.

What micron sizing do you use for the primary and secondary?


--
"j" ganz @@
www.sailnow.com

Changed my mind about fuel polishing
 

Rodger,
For what it is worth, I have two 1000 liter tanks, one starboard and one
port. The plan is to fill one, polish that into the other and then fill the
now empty tank. I then fill the day tank from the "clean" tank. As fuel is
consumed, I then transfer from the dirty tank to the clean tank for balance.
My transfer system is fed by a manifold and it also pumps to an outlet
manifold. Each manifold has three ball valves, which allows me to pump from
and to any of the three tanks. I use a large RACOR centrifugal filter and a
surplus US Army helicopter fuel transfer pump.
Steve

"Roger Long" wrote in message
...
The sediment bowl on the Shelco filter I put in for my fuel polishing (or
Pre-filtering, whatever you want to call it) system doesn't drain
completely. I took it out of the boat today, poured off the fuel (Not a
drop of water BTW), and scraped out the stuff in the bottom:

http://home.maine.rr.com/rlma/Crud.jpg

Wow. I was saying a while ago that didn't think the system was necessary
for the cruising I do now. I would have agreed with anyone who said it
was a hobby affectation. I still wouldn't say "necessary" is quite the
right word but I sure am glad I have it just for tootling around in Maine.

This is the left overs from about 100 gallons of fuel purchased during the
year and isn't all off it since a gust of wind blew the plate over. About
half of the fuel was road diesel purchased at a high volume gas station.
Sure, the Racor could have dealt with this stuff and I could have dealt
with the Racor but, why? There was not a speck in the Racor bowl it
looked just like it did when I changed the filter and filled the sytem
last spring. Having this crud removed from the system in a way that makes
having to deal with it's disposal underway vanishingly unlikely is great.

--
Roger Long

Changed my mind about fuel polishing
 

"Capt. JG" wrote

No... didn't miss it. He's dealing with bio/water issues every day. I
think I'll trust his experience, although he didn't say to be obsessive
about it. He's advocating exactly that... minimizing the surface area.

But he's missing out on the frequent opportunity to have the sloshing of a
partially full fuel tank knock off some bio film sticking to the sides.
He's also increasing the average age of the fuel with its absorbed water
content and oxidation. I've been working with commercial boat operators for
nearly four decades and never heard of trying to keep fuel tanks topped up
until this newsgroup.

The yard manager I brought my non-running engine to when the boat arrived in
Portland had similar or more experience. He successfully diagnosed that all
it needed was a thorough cleaning after the Yamaha shop and dealer in MI
told me it needed two new injectors and possibly an injector pump. The
engine has been running perfectly for three seasons on those components.
That gives him a lot of street cred in my book. His position on fuel was
that you should use up as much as you can before refueling so that most of
what you are burning is as fresh as possible. Why do experienced people
differ on points like this? Because it doesn't make much difference.
Topping off might make sense for the once a month weekender but would be
crazy for the almost daily sailor such as myself whether it was going to the
fuel dock and standing in line, doing the docking and undocking, etc., for a
gallon or lugging a can all the way down the dock at the end of the sailing
day when tired guests want to get home. The fuel sitting in that can is as
likely to go bad as what is in the tank. Do you keep topping up the can
that you top up the tank with? Where does it end?

What micron sizing do you use for the primary and secondary?

The Racor primary is 2 Mu because the polishing system keeps much crud from
every reaching it and it is oversized for the engine so there is no downside
to the finer element. It's pressure fed by the electric fuel pump.

The secondary is a Yamaha engine mounted filter and probably 10 Mu. Since
only their elements fit, I have to buy whatever they supply for the engine
anyway.

The polishing filter is 10 Mu but, as Rich H points out, will take out
smaller stuff because the fuel goes through it many times and it is a depth
filter instead of a surface filter. It also gets finer as it loads up.

--
Roger Long

Changed my mind about fuel polishing
 

I'm glad there is someone out there more compulsive about fuel treatment
than I am:)

--
Roger Long

Changed my mind about fuel polishing
 

"Roger Long" wrote in message
...
"Capt. JG" wrote

No... didn't miss it. He's dealing with bio/water issues every day. I
think I'll trust his experience, although he didn't say to be obsessive
about it. He's advocating exactly that... minimizing the surface area.

But he's missing out on the frequent opportunity to have the sloshing of a
partially full fuel tank knock off some bio film sticking to the sides.
He's also increasing the average age of the fuel with its absorbed water
content and oxidation. I've been working with commercial boat operators
for nearly four decades and never heard of trying to keep fuel tanks
topped up until this newsgroup.

Water absorption in diesel? Seems to me that would be a very, very small
issue, given that they don't mix. If the bio is stuck to the sides, why
would you want to knock it free? Better to kill it, filter the fuel and be
done. Do commercial boat operators let their boats sit for weeks at a time?
Seems to me that they would use their engines frequently, then fillerup,
then repeat. Thus, they are, in a sense, topping up, except the fuel is
lower when they start.

The yard manager I brought my non-running engine to when the boat arrived
in Portland had similar or more experience. He successfully diagnosed
that all it needed was a thorough cleaning after the Yamaha shop and
dealer in MI told me it needed two new injectors and possibly an injector
pump. The engine has been running perfectly for three seasons on those
components. That gives him a lot of street cred in my book. His position
on fuel was that you should use up as much as you can before refueling so
that most of what you are burning is as fresh as possible. Why do
experienced people differ on points like this? Because it doesn't make
much difference. Topping off might make sense for the once a month
weekender but would be crazy for the almost daily sailor such as myself
whether it was going to the fuel dock and standing in line, doing the
docking and undocking, etc., for a gallon or lugging a can all the way
down the dock at the end of the sailing day when tired guests want to get
home. The fuel sitting in that can is as likely to go bad as what is in
the tank. Do you keep topping up the can that you top up the tank with?
Where does it end?

Well, that's what I'm talking about... the once-a-month or slightly more
use. I've had the same diesel, less one topping off, for two years. I
haven't detected any difference in performance, so I don't think the
degradation issue is real (enough).

Ummm... my dock box is about 2 feet from my boat. I have a cart to move the
jug of fuel if I can't lift 3 gallons? Seems pretty easy.

What micron sizing do you use for the primary and secondary?

The Racor primary is 2 Mu because the polishing system keeps much crud
from every reaching it and it is oversized for the engine so there is no
downside to the finer element. It's pressure fed by the electric fuel
pump.

The secondary is a Yamaha engine mounted filter and probably 10 Mu. Since
only their elements fit, I have to buy whatever they supply for the engine
anyway.

The polishing filter is 10 Mu but, as Rich H points out, will take out
smaller stuff because the fuel goes through it many times and it is a
depth filter instead of a surface filter. It also gets finer as it loads
up.




--
"j" ganz @@
www.sailnow.com

Changed my mind about fuel polishing
 

On Nov 16, 1:29*pm, "Roger Long" wrote:
"Capt. JG" wrote



No... didn't miss it. He's dealing with bio/water issues every day. I
think I'll trust his experience, although he didn't say to be obsessive
about it. He's advocating exactly that... minimizing the surface area.

But he's missing out on the frequent opportunity to have the sloshing of a
partially full fuel tank knock off some bio film sticking to the sides.
He's also increasing the average age of the fuel with its absorbed water
content and oxidation. *I've been working with commercial boat operators for
nearly four decades and never heard of trying to keep fuel tanks topped up
until this newsgroup.

The yard manager I brought my non-running engine to when the boat arrived in
Portland had similar or more experience. *He successfully diagnosed that all
it needed was a thorough cleaning after the Yamaha shop and dealer in MI
told me it needed two new injectors and possibly an injector pump. * The
engine has been running perfectly for three seasons on those components.
That gives him a lot of street cred in my book. His position on fuel was
that you should use up as much as you can before refueling so that most of
what you are burning is as fresh as possible. *Why do experienced people
differ on points like this? Because it doesn't make much difference.
Topping off might make sense for the once a month weekender but would be
crazy for the almost daily sailor such as myself whether it was going to the
fuel dock and standing in line, doing the docking and undocking, etc., for a
gallon or lugging a can all the way down the dock at the end of the sailing
day when tired guests want to get home. *The fuel sitting in that can is as
likely to go bad as what is in the tank. *Do you keep topping up the can
that you top up the tank with? *Where does it end?

What micron sizing do you use for the primary and secondary?

The Racor primary is 2 Mu because the polishing system keeps much crud from
every reaching it and it is oversized for the engine so there is no downside
to the finer element. *It's pressure fed by the electric fuel pump.

The secondary is a Yamaha engine mounted filter and probably 10 Mu. *Since
only their elements fit, I have to buy whatever they supply for the engine
anyway.

The polishing filter is 10 Mu but, as Rich H points out, will take out
smaller stuff because the fuel goes through it many times and it is a depth
filter instead of a surface filter. *It also gets finer as it loads up.

--
Roger Long

I tend to keep my day tanks topped up and clean. with just under
10,000 gal in the main tanks we simply filter as we dispence to the
small boats or our day tanks. we filter when we fill so we dont get a
bug problem from the fuel barges or docks. but that on a boat with
lots of fuel.

Changed my mind about fuel polishing
 

Roger

Glad you noted the crud in the bottom of the Shelco housing.... this
debris is/are the nucleation sites upon which such particle grow/
agglomerate.
Full or topped-off tanks - never unless Im travelling. Water in oil
is in two phases: 1. sensible (free) water that drops out by gravity,
2. water that is emusified (bound) in the oil.
Fuel oil that is long term exposed to atmosphere saturated with water
(from vapor) will eventually settle out in the bottom of the tank. I
never ever 'top off' a tank unless I plan to use most of it in the
short term. Why store the oil in a tank with an atmospheric vent only
to have it uptake water (vapor), etc.? Simple solution is only upload
what you need plus some reserve; if storing long term, drain the oil
and burn it in your home heater as EMPTY tanks dont 'condense'
water.

The probable chief organism that thrives in fuel oil tanks is
Cladosporium Resinae - ***a fungus*** that is spread by spores ...
most probably aspirated through the tank VENT pipe. Currently Im
using a bio-blocking 0,2µM abs PTFE membrane filter capsule on my vent
and will compare the tank innards on my next scheduled clean-out (in 2
years). Million gallon field fuel tanks rarely become contaminated;
its the teeny boat tanks that usually have the particulate/
contamination problems.

Im currently travelling and using a lot of fuel so Ive temporarily
removed the desiccant vapor trap on the vent line.

regards to all.

Changed my mind about fuel polishing
 

On Sun, 16 Nov 2008 16:30:04 -0500, "Roger Long"
wrote:

I'm glad there is someone out there more compulsive about fuel treatment
than I am:)

Nothing wrong with discussing it and taking the precautions you have.
Cheap insurance.
Not nearly as bad as the Honda freaks changing their brake fluid every
year or two because brake fluid is "Hygroscopic."
We'll let you know when you step over the anal line.

--Vic

Changed my mind about fuel polishing
 

"RichH" wrote

Why store the oil in a tank with an atmospheric vent only to have it uptake
water (vapor), etc.?

Exactly.

Please confirm that I'm correct in the advice to others (some outside the
newsgroup) that there is no point in filling the tank unless it's filled up
into the vent so that the surface area of fuel available for water vapor
transfer is the cross section of the vent pipe and not the whole top of the
tank.

Since this is impractical in many vessels and impractical in most normal
operation, the whole topping up the tank thing is a crock.

I'm going to put a desiccant vapor trap on my sounding tube for the winter
which is easy to do and tape over the vent.

--
Roger Long

Changed my mind about fuel polishing
 

"Capt. JG" wrote

Water absorption in diesel? Seems to me that would be a very, very small
issue, given that they don't mix.

But they do. See Rich H post below.

If the bio is stuck to the sides, why would you want to knock it free?

So that it can get into the filters to be removed and not come off at an
inconvienient time. Biocide is just a way of assisting its removal but the
stuff is nasty and tends to dump a lot of stuff into your filter system all
at once if the tank is badly fouled. The mechanical action of slack tanks
gets some of it into the system more gradually; especially with some
assistance from something like StarTron.

Keeping the tank "topped up" to the extent practical in normal operation
usually means that there will be full air and water vapor access to the
entire surface of the fuel. The difference between that and a slack tank is
insignificant (for a nearly straight sided tank) and, as Rich points out,
more fuel volume for the same air/fuel contact area means more water
absorbtion.

--
Roger Long

Changed my mind about fuel polishing
 

The issue of one 'sludging' ones filters from a cruddy tank is more
than just a 'fine point'. Just earlier this year, supposedly a Brit
lost his boat onto the jetty into Charleston SC Harbor when his engine
failed and he got caught in the rage of the inlet.

..... and for that very reason its a good idea to have a well
maintained fuel system, even a few gallon 'day tank' that holds back a
few gallons all 'ready to go' in case of such an event. The more and
more I think of it a small reserve tank of a few gallons makes all the
sense in the world - enabling one to motor on an hour or two; instead
of power-puking into the bilge while trying to change a damn filter
set. :-)

Changed my mind about fuel polishing
 

That constantly replenishing emergency tank idea of yours is one of the best
I've seen in this group. I'm still trying to figure out how I might
implement it but space, even for just the gallon I would need, is pretty
tight in a 32 foot boat.

I think it's very long odds that that the big Shelco filter would suddenly
load up. I would have advance warning from the Racor flow stopping and it
ought to take a lot longer for the Shelco to become critical. If I had to
change out a Racor filter, I would focus on getting into a safer position.
I also have two tanks so switching to the other one as well as switching the
fuel supply to the polishing output would be part of the drill if the Racor
loaded up. I'm a sailboat as well so I usually have an alternative
propulsion source.

--
Roger Long

Changed my mind about fuel polishing
 

Please confirm that I'm correct in the advice to others (some outside the
newsgroup) that there is no point in filling the tank unless it's filled up
into the vent so that the surface area of fuel available for water vapor
transfer is the cross section of the vent pipe and not the whole top of the
tank.

Since this is impractical in many vessels and impractical in most normal
operation, the whole topping up the tank thing is a crock.

I'm going to put a desiccant vapor trap on my sounding tube for the winter
which is easy to do and tape over the vent.

--
Roger Long

Here's a website that gives a brief tech description of what is
happening .... sorry that its JetFuel but the same happens with
diesel, etc.:
http://www.flowmeterdirectory.com/fl..._07082401.html

My professional (filtration engineering) work in this area has
included the ultra-pure ultra-dehydrated oils used in high voltage
transformers, contactors and tap changers ... although sealed,
eventually become contaminated with water (free, dissolved and
emuslified) which radically changes the dielectric strength of the
oil. The water uptake is all by 'chemical equilibrium'; you put in
ultra-dehydrated oil - come back in 2-3 years and remove the water
( or replace the equipment if if shorts out due to the water and
generated particles). Simple physical-chemical equilibrium at work.

Bruce reported using oil that was barreled in WWII. Entirely possible
if the barrel was filled at temperature that sterilized the contents,
is totally sealed, no water entered, and no fungal spores got in.
After all, that oil is zillions of years old and it stayed in the
ground because no microorganism used it as a nutrient source, etc.

Changed my mind about fuel polishing
 

"Roger Long" wrote in message
...
"Capt. JG" wrote

Water absorption in diesel? Seems to me that would be a very, very small
issue, given that they don't mix.

But they do. See Rich H post below.

If the bio is stuck to the sides, why would you want to knock it free?

So that it can get into the filters to be removed and not come off at an
inconvienient time. Biocide is just a way of assisting its removal but
the stuff is nasty and tends to dump a lot of stuff into your filter
system all at once if the tank is badly fouled. The mechanical action of
slack tanks gets some of it into the system more gradually; especially
with some assistance from something like StarTron.

Star Tron disperses the bacteria, but it doesn't do anything for a badly
fouled tank. If you're talking about a tank that's pretty good, maintained
with good fuel and you're careful about water egress, then the amount of
bacteria stuck to the sides would be minimal. In fact, they would die when
covered with fuel, and then they would pass naturally out of the tank. If
action is needed to get the bacteria out, I would much rather take that
action in a known timeframe vs. have it slowly clog a filter. If you're
going that route, then get a pressure gauge and put it on the filter. Then,
you'll know when the bacteria are starting to clog it. I can't imagine
wanting the sloshing action to break loose a bunch of decent size pieces and
have it immediately kill the engine.

If one has a badly fouled tank, that needs to be dealt with next to the
dock, not at sea.

Keeping the tank "topped up" to the extent practical in normal operation
usually means that there will be full air and water vapor access to the
entire surface of the fuel. The difference between that and a slack tank
is insignificant (for a nearly straight sided tank) and, as Rich points
out, more fuel volume for the same air/fuel contact area means more water
absorbtion.

I don't understand. If the tank if full, it's full. If you're using the
engine, you're using the engine, and when you get back and top it off with a
couple of gallons, it's full again, and whatever bacteria is alive for that
brief period when it's not full will quickly die and drop to the bottom. I
also don't understand the "absorption" issue with diesel. The diesel and
water don't mix, so whatever there is would be minimal to say the least and
it certainly won't hold bacteria.


--
"j" ganz @@
www.sailnow.com

Changed my mind about fuel polishing
 

"The diesel and water don't mix"
NOT so.

Water to a small amount dissolves in diesel
Diesel to a small amount dissolves in water
Emulsions are formed between the two phases of oil and water ... and
disperse throughout the oil

Only FREE water doesnt mix with water as it has gravimetrically
settled out of the oil due to gravity.


THREE phases of water in oil: Free water, dissolved water, emulsified
water.

Changed my mind about fuel polishing
 

This whole subject could be easily put to bed by calling your local
fuel polisher and asking the age of boats that need polishing.
I think you'll find all the 70's and 80's need cleaning and the 90's
will need cleaning in the next few years. Anything newer and there is no
problem. Meaning that if your system is clean, it's probably good for 20
years. At least, that's the way it is in the Puget Sound area. I suppose
warmer, more humid areas could be worse.
That said, I run dual Racors mainly because they were freebies and my
neighbor polished my fuel when I installed the Racors.

Gordon

Changed my mind about fuel polishing
 

"RichH" wrote in message
...
"The diesel and water don't mix"
NOT so.

Water to a small amount dissolves in diesel
Diesel to a small amount dissolves in water
Emulsions are formed between the two phases of oil and water ... and
disperse throughout the oil

Only FREE water doesnt mix with water as it has gravimetrically
settled out of the oil due to gravity.


THREE phases of water in oil: Free water, dissolved water, emulsified
water.


Some amount of my skin molecules become part of my computer keyboard and vis
versa. This is meaningless in the scheme of things for both me, my keyboard,
and for diesel/water in a tank. If it wasn't meaningless, the engine would
quit or wouldn't run to begin with. This doesn't happen unless the fuel is
contaminated (and the amount of water you describe clearly isn't enough in
most situations), the engine can't get enough air, or the fuel filter/line
is clogged. If you want to further limit the emulsification, then limit the
sloshing, which is exactly what a full or near full tank will do.

I stand by my original statement for real-world, sailboat applications.

--
"j" ganz @@
www.sailnow.com

Changed my mind about fuel polishing
 

"Gordon" wrote in message
m...

This whole subject could be easily put to bed by calling your local fuel
polisher and asking the age of boats that need polishing.
I think you'll find all the 70's and 80's need cleaning and the 90's will
need cleaning in the next few years. Anything newer and there is no
problem. Meaning that if your system is clean, it's probably good for 20
years. At least, that's the way it is in the Puget Sound area. I suppose
warmer, more humid areas could be worse.
That said, I run dual Racors mainly because they were freebies and my
neighbor polished my fuel when I installed the Racors.

Gordon


This is exactly what the guy with 30+ years of experience said on Saturday.
My boat/tank is over 30 years old and doesn't have dual. I haven't and
neither did the original owner keep the tank topped off. I've never had a
bacterial contamination issue, but I would certainly like to avoid one. It
was recommended to add a dual, add a biocide, add a cetane enhancer, and try
to keep the tank topped. I think I'll take his recommendations, given his
years of experience and world-wide reputation.

No put down on anyone else intended. But, I think I'll use the Occam's Razor
approach. His advice is simple and makes sense.

--
"j" ganz @@
www.sailnow.com

Changed my mind about fuel polishing
 

On Sun, 16 Nov 2008 20:39:13 -0500, "Roger Long"
wrote:

That constantly replenishing emergency tank idea of yours is one of the best
I've seen in this group. I'm still trying to figure out how I might
implement it but space, even for just the gallon I would need, is pretty
tight in a 32 foot boat.

I think it's very long odds that that the big Shelco filter would suddenly
load up. I would have advance warning from the Racor flow stopping and it
ought to take a lot longer for the Shelco to become critical. If I had to
change out a Racor filter, I would focus on getting into a safer position.
I also have two tanks so switching to the other one as well as switching the
fuel supply to the polishing output would be part of the drill if the Racor
loaded up. I'm a sailboat as well so I usually have an alternative
propulsion source.

A friend built a day tank in his old boat. He used a small electric
fuel pump as a transfer pump to fill the tank and piped the
overflow/breather line back to his main fuel tank.

He said he usually remembered to turn the transfer pump off but if he
didn't the overflow just returned to the main tank.
Cheers,

Bruce
(bpaige125atgmaildotcom)

Changed my mind about fuel polishing
 

"Capt. JG" wrote

This is exactly what the guy with 30+ years of experience said on
Saturday. It was recommended to add a dual (filter)....

So you are going to add that second filter ARE you not? In view of the high
current conditions in SF Bay and your responsibility to your students I'd
hate to be you if something happened due to fuel contamination after posting
that you were aware of this recommendation.

While you are at it, consider this:

I think my system has gotten a bad rap for complexity due to the dual tanks
which does drive up the cost and complexity a lot. Here is what it would
look like in yours or the typical single tank boat:

http://home.maine.rr.com/rlma/1tankFOsystem.gif

The Shelco Filter was about the same cost as a Racor. The second pump was
about 60 bucks and is also a good redundancy feature. This redundancy would
be especially desirable in a boat with a low mounted tank that will not
gravity feed. Otherwise, there are only one or two additional valves and a
few fittings more than in the dual filter system. The cost difference is
insignificant in boat bucks.

Fuel contamination and degradation is always going on to some extent. This
system is constantly removing it whenever the engine is running. The system
will filter a volume equal to the typical sailboat tank every hour of
running time. Your dual filter OTOH is just sitting there doing nothing
useful.

Fuel flow at the tank inlet is vastly greater than in the typical system.
This increases the uptake of water and anything else floating around in the
bottom of the tank waiting for rough water and a tight spot to get sucked
into the system at the worst possible time. Since most of the fuel is going
through the polishing filter and being returned to the tank, getting this
stuff into the fuel system is a good thing.

In the event of the primary filter (Racor on the drawing) loading up, OR the
primary fuel pump failing, just turn one valve and you are back in business
with full fuel flow. Some tank configurations or engine driven fuel pump
problems may require partially or completely closing the second valve. In
any event, it doesn't take any longer than switching filters.

Let's say you do pick up a load of bad fuel and calling a fuel polishing
contractor isn't an option either because you are cruising or there isn't
one as is now the case here in Portland. (BTW, none of this has anything
to do with an old and neglected tank that has gotten thouroughly coated and
filled with slime. That's a different issue all together.)

Duel Filter Setup:

Switch filter.
Change first filter element - 16 bucks.

Run for a while.

Repeat as often as necessary at about 16 bucks a filter element.

The only way to get fuel flow is to run the engine That means doing these
repeated and expensive filter changes underway or with the engine running at
the dock and sucking very little fuel. With an engine the size you have on
your boat, it will take 20 - 30 hours to run all the fuel through the
filters. And, you have to consume it which adds to the expense.

Polishing Setup:

Turn red valve and isolation valve if necessary and deal with it when you
get back to the dock. The high capacity of the Shelco makes its load up
time much higher than the Racor or similary filter. You can change it's two
buck element while the engine runs on the Racor, just as on a dual filter
system if it does load up.

When you get back to the dock, you can plug into shore power and let the
polishing system run with the engine off, changing two dollar filter
elements as necessary.

Based on the amount of crud I found in my Shelco and the pristine condition
of the sediment bowl in my Racor, I would say loading up of the Racor is
unlikely in any event.

Here's a challenge. Usually after you've taken a seminar like the one you
just did, they will entertain a few follow up questions. Take this
schematic to your guy and let us know what he thinks.

--
Roger Long

Changed my mind about fuel polishing
 

"Roger Long" wrote in message
...
"Capt. JG" wrote

This is exactly what the guy with 30+ years of experience said on
Saturday. It was recommended to add a dual (filter)....

So you are going to add that second filter ARE you not? In view of the
high current conditions in SF Bay and your responsibility to your students
I'd hate to be you if something happened due to fuel contamination after
posting that you were aware of this recommendation.

I probably will. I need to haul out in the next couple of months, and given
"fandamily" stuff coming up... Turkey/Xmas, I probably won't be teaching on
her until after the haul.

The thing is... I don't really use the engine all that much during much of a
class. I'm pretty careful about doing all the preliminary checks, which are
part of the typical class. The basic class I teach has the first 1/2 day +
as engine awareness/use, and for that we're typically in and around a
marina. The only time the engine has quit unexpectedly was when a student
throttled back so much that the engine died... throttle is the kill switch
for my boat. This actually happend during the last class when we were
practicing motoring up to and stopping at a mooring. Engine quit, no
problem. I popped the jib and we sailed off in two seconds flat.

While you are at it, consider this:

I think my system has gotten a bad rap for complexity due to the dual
tanks which does drive up the cost and complexity a lot. Here is what it
would look like in yours or the typical single tank boat:

http://home.maine.rr.com/rlma/1tankFOsystem.gif

The Shelco Filter was about the same cost as a Racor. The second pump was
about 60 bucks and is also a good redundancy feature. This redundancy
would be especially desirable in a boat with a low mounted tank that will
not gravity feed. Otherwise, there are only one or two additional valves
and a few fittings more than in the dual filter system. The cost
difference is insignificant in boat bucks.

Fuel contamination and degradation is always going on to some extent.
This system is constantly removing it whenever the engine is running. The
system will filter a volume equal to the typical sailboat tank every hour
of running time. Your dual filter OTOH is just sitting there doing
nothing useful.

Fuel flow at the tank inlet is vastly greater than in the typical system.
This increases the uptake of water and anything else floating around in
the bottom of the tank waiting for rough water and a tight spot to get
sucked into the system at the worst possible time. Since most of the fuel
is going through the polishing filter and being returned to the tank,
getting this stuff into the fuel system is a good thing.

True, but in the SF bay, "rough" sailing (bouncing around) is pretty
typical. Always looking for the zephyr, but... well, it happens, hopefully
around lunch time. LOL

In the event of the primary filter (Racor on the drawing) loading up, OR
the primary fuel pump failing, just turn one valve and you are back in
business with full fuel flow. Some tank configurations or engine driven
fuel pump problems may require partially or completely closing the second
valve. In any event, it doesn't take any longer than switching filters.

Let's say you do pick up a load of bad fuel and calling a fuel polishing
contractor isn't an option either because you are cruising or there isn't
one as is now the case here in Portland. (BTW, none of this has anything
to do with an old and neglected tank that has gotten thouroughly coated
and filled with slime. That's a different issue all together.)

Geez... I hope not around here. The big issue is whether or not the fuel
pump attendant is around so I can pay him. Early in the summer, he wasn't...
pumps were unlocked and there were two of us standing around for a while to
see if he would return. Finally, we just left the cash in the office (also
unlocked).

Last I pulled the single filter from the primary, I almost didn't replace it
because it looked so good...

Duel Filter Setup:

Switch filter.
Change first filter element - 16 bucks.

Run for a while.

Repeat as often as necessary at about 16 bucks a filter element.

The only way to get fuel flow is to run the engine That means doing these
repeated and expensive filter changes underway or with the engine running
at the dock and sucking very little fuel. With an engine the size you
have on your boat, it will take 20 - 30 hours to run all the fuel through
the filters. And, you have to consume it which adds to the expense.

Polishing Setup:

Turn red valve and isolation valve if necessary and deal with it when you
get back to the dock. The high capacity of the Shelco makes its load up
time much higher than the Racor or similary filter. You can change it's
two buck element while the engine runs on the Racor, just as on a dual
filter system if it does load up.

When you get back to the dock, you can plug into shore power and let the
polishing system run with the engine off, changing two dollar filter
elements as necessary.

Based on the amount of crud I found in my Shelco and the pristine
condition of the sediment bowl in my Racor, I would say loading up of the
Racor is unlikely in any event.

Here's a challenge. Usually after you've taken a seminar like the one you
just did, they will entertain a few follow up questions. Take this
schematic to your guy and let us know what he thinks.

I'll see what I can do. I copied out the schematic and I'll email it to him,
along with your explanation.

--
"j" ganz @@
www.sailnow.com

Changed my mind about fuel polishing
 

On Nov 17, 6:04*am, "Roger Long" wrote:
"Capt. JG" wrote

This is exactly what the guy with 30+ years of experience said on
Saturday. It was recommended to add a dual (filter)....

So you are going to add that second filter ARE you not? *In view of the high
current conditions in SF Bay and your responsibility to your students I'd
hate to be you if something happened due to fuel contamination after posting
that you were aware of this recommendation.

While you are at it, consider this:

I think my system has gotten a bad rap for complexity due to the dual tanks
which does drive up the cost and complexity a lot. *Here is what it would
look like in yours or the typical single tank boat:

http://home.maine.rr.com/rlma/1tankFOsystem.gif

The Shelco Filter was about the same cost as a Racor. *The second pump was
about 60 bucks and is also a good redundancy feature. *This redundancy would
be especially desirable in a boat with a low mounted tank that will not
gravity feed. * Otherwise, there are only one or two additional valves and a
few fittings more than in the dual filter system. The cost difference is
insignificant in boat bucks.

Fuel contamination and degradation is always going on to some extent. *This
system is constantly removing it whenever the engine is running. *The system
will filter a volume equal to the typical sailboat tank every hour of
running time. *Your dual filter OTOH is just sitting there doing nothing
useful.

Fuel flow at the tank inlet is vastly greater than in the typical system.
This increases the uptake of water and anything else floating around in the
bottom of the tank waiting for rough water and a tight spot to get sucked
into the system at the worst possible time. *Since most of the fuel is going
through the polishing filter and being returned to the tank, getting this
stuff into the fuel system is a good thing.

In the event of the primary filter (Racor on the drawing) loading up, OR the
primary fuel pump failing, just turn one valve and you are back in business
with full fuel flow. *Some tank configurations or engine driven fuel pump
problems may require partially or completely closing the second valve. *In
any event, it doesn't take any longer than switching filters.

Let's say you do pick up a load of bad fuel and calling a fuel polishing
contractor isn't an option either because you are cruising or there isn't
one as is now the case here in Portland. * (BTW, none of this has anything
to do with an old and neglected tank that has gotten thouroughly coated and
filled with slime. *That's a different issue all together.)

Duel Filter Setup:

Switch filter.
Change first filter element - 16 bucks.

Run for a while.

Repeat as often as necessary at about 16 bucks a filter element.

The only way to get fuel flow is to run the engine *That means doing these
repeated and expensive filter changes underway or with the engine running at
the dock and sucking very little fuel. *With an engine the size you have on
your boat, it will take 20 - 30 hours to run all the fuel through the
filters. *And, you have to consume it which adds to the expense.

Polishing Setup:

Turn red valve and isolation valve if necessary and deal with it when you
get back to the dock. *The high capacity of the Shelco makes its load up
time much higher than the Racor or similary filter. *You can change it's two
buck element while the engine runs on the Racor, just as on a dual filter
system if it does load up.

When you get back to the dock, you can plug into shore power and let the
polishing system run with the engine off, changing two dollar filter
elements as necessary.

Based on the amount of crud I found in my Shelco and the pristine condition
of the sediment bowl in my Racor, I would say loading up of the Racor is
unlikely in any event.

Here's a challenge. *Usually after you've taken a seminar like the one you
just did, they will entertain a few follow up questions. *Take this
schematic to your guy and let us know what he thinks.

--
Roger Long

Roger why not double the filters and install a two position Y valve
them so you can shut off the clogged filter and run through a new
instead of trying to change out while running?

Changed my mind about fuel polishing
 

"Two meter troll" wrote

Roger, why not double the filters and install a two position Y valve
them so you can shut off the clogged filter and run through a new
instead of trying to change out while running?

Did you read the post? The boat will run on the Shelco filter and polishing
pump until that filter loads up which will take a lot, lot, longer than a
second Racor to become non-functional.

Or, do you mean having 4 filters?

--
Roger Long

Changed my mind about fuel polishing
 

On 2008-11-16 22:48:36 -0500, Gordon said:

I think you'll find all the 70's and 80's need cleaning and the 90's
will need cleaning in the next few years. Anything newer and there is
no problem. Meaning that if your system is clean, it's probably good
for 20 years. At least, that's the way it is in the Puget Sound area. I
suppose warmer, more humid areas could be worse.

It's not that cut-and-dry. I had occasion to empty our tank to put in
fuel level sensors and such for a few seasons.

In one early-half season, we picked up enough bugs to clog our filter,
but once that lot was filtered out, we've not had a problem. A season
or two later, it was still bright and shiny.

I expect we've a few bugs at the moment, but I don't think we've used
20 gallons (from a 15 gallon tank) in 3 seasons. Lots of time to breed
the critters. Turn-over, biocide, and filtering all contribute to
cleanliness; the obverse is also true.

Amending slightly: Roger's experience from lots of turnover indicates
to me that he got some gunky stuff from the supplying fuel tanks. As
much as he burned, there really wasn't that much time to breed the
critters onboard.

--
Jere Lull
Xan-à-Deux -- Tanzer 28 #4 out of Tolchester, MD
Xan's pages: http://web.mac.com/jerelull/iWeb/Xan/
Our BVI trips & tips: http://homepage.mac.com/jerelull/BVI/

Changed my mind about fuel polishing
 

"Jere Lull" wrote

Amending slightly: Roger's experience from lots of turnover indicates to
me that he got some gunky stuff from the supplying fuel tanks. As much as
he burned, there really wasn't that much time to breed the critters
onboard.


I strongly suspect that is the case. One of the last loads of the season
was from a looong marina hose. There was probably the half tank I put in
just in the hose alone which had been sitting out in the sun since the last
boat came along. It was late in the year and the dock attendant mentioned
that it had been a while since anyone came in for diesel.

This is exactly the situation that prompted the installation. When I get to
where fuel docks are few and far between, I might have to take on a load
even if it looks funky. Or, the sample might look good and bad stuff comes
down the hose later. With the standard filter set up, even if dual, there
is no choice but to filter it all at the engine consumption rate, burn it
immediately after it goes through the filter, and change filters through the
whole tank. People have used up enough Racor filter elements in these cases
to pay for my Shelco filter and the second pump.

The one drawback of my system is that, in an extreme case, both filters
could plug up with nothing to switch to. The Shelco has very high retention
capacity though compared to the Racor. The Racor would almost certainly
plug first in that case and I would open the bypass from the polishing
system. Extra caution right after fueling and attention to the gauges on the
filters before getting into a critical situation should be SOP with either
system.

If I do find I have a problem, it can be dealt with without having to run
fuel through the engine or even having the engine running and I can get
multiple passes through the filter before sending fuel to the engine.
That's the real beauty of the system.

--
Roger Long

Changed my mind about fuel polishing
 

On Tue, 18 Nov 2008 13:48:43 -0500, "Roger Long"
wrote:

This is exactly the situation that prompted the installation. When I get to
where fuel docks are few and far between, I might have to take on a load
even if it looks funky.

Get thee a Baja Filter or West Marine's equivalent. They were
designed for taking on suspect fuel in funky locations:

http://www.practical-sailor.com/sample/Fuelfilter.html

Changed my mind about fuel polishing
 

"Wayne.B" wrote

Get thee a Baja Filter or West Marine's equivalent. They were
designed for taking on suspect fuel in funky locations:

http://www.practical-sailor.com/sample/Fuelfilter.html


I've got one (West) but it's hard to use on my boat and busy fuel docks
aren't always happy with the extra fueling time. There are also ways
contamination can get in. They take out water but I'm not sure about fungal
spores which can also come in the vent.

--
Roger Long

Changed my mind about fuel polishing
 

On Nov 17, 1:10*pm, "Roger Long" wrote:
"Two meter troll" wrote

Roger, why not double the filters and install a two position Y valve
them so you can shut off the clogged filter and run through a new
instead of trying to change out while running?

Did you read the post? *The boat will run on the Shelco filter and polishing
pump until that filter loads up which will take a lot, lot, longer than a
second Racor to become non-functional.

Or, do you mean having 4 filters?

--
Roger Long

four filters. two sets paired with a y valve so you can run through
one or the other in the set. it would save you changing out filters in
bad weather (which IME is when filters clog up) or while running.

Changed my mind about fuel polishing
 

Two meter troll wrote:

four filters. two sets paired with a y valve so you can run through
one or the other in the set. it would save you changing out filters in
bad weather (which IME is when filters clog up) or while running.

That would certainly increase redundancy but, so would a third set of
filters. It has to end somewhere on a 32 foot boat.

The reason filters clog up in bad weather is because the motion of the boat
stirs up the stuff that's been sitting in the bottom of the tank. The whole
point of the polishing system is to remove that stuff before you get into
bad weather. Before bad weather or going into a spot where power is vital,
it would be good to take a peek at the filter gauges to see if they show any
restriction. This would be an especially good thing to do with a new load
of fuel.

With the high capacity of the Shelco filter, it's pretty unlikely I'll be
changing elements underway.

--
Roger Long

Changed my mind about fuel polishing
 

On Nov 19, 3:28*pm, "Roger Long" wrote:
Two meter troll wrote:
four filters. two sets paired with a y valve so you can run through
one or the other in the set. it would save you changing out filters in
bad weather (which IME is when filters clog up) or while running.

That would certainly increase redundancy but, so would a third set of
filters. It has to end somewhere on a 32 foot boat.

The reason filters clog up in bad weather is because the motion of the boat
stirs up the stuff that's been sitting in the bottom of the tank. *The whole
point of the polishing system is to remove that stuff before you get into
bad weather. *Before bad weather or going into a spot where power is vital,
it would be good to take a peek at the filter gauges to see if they show any
restriction. *This would be an especially good thing to do with a new load
of fuel.

With the high capacity of the Shelco filter, it's pretty unlikely I'll be
changing elements underway.

--
Roger Long
IME the fuel polishing only works for stuff suspendid in normal
conditions; I have never seen a tank that didnt have stuff in the
bottom that only got into the filters in really bad conditions.
As you say. Me I like redundancy when I can get it.

Changed my mind about fuel polishing
 

Two meter troll wrote:

IME the fuel polishing only works for stuff suspendid in normal
conditions; I have never seen a tank that didnt have stuff in the
bottom that only got into the filters in really bad conditions.
As you say. Me I like redundancy when I can get it.

You have to remember that the polishing pump is drawing at 20 - 30 times the
rate of the normal fuel pump. That makes it much more effective at sucking
stuff up out of the bottom of the tank. With my retrofitted system, both
engine and polishing flow are drawn through the same suction. I actually
can't draw a tank quite as low with the polishing system running as I can
with just the engine drawing because it sucks air down about an inch and
into the intake.

--
Roger Long

Changed my mind about fuel polishing
 

On Nov 19, 7:28*pm, "Roger Long" wrote:
Two meter troll wrote:
IME the fuel polishing only works for stuff suspendid in normal
conditions; I have never seen a tank that didnt have stuff in the
bottom that only got into the filters in really bad conditions.
As you say. Me I like redundancy when I can get it.

You have to remember that the polishing pump is drawing at 20 - 30 times the
rate of the normal fuel pump. *That makes it much more effective at sucking
stuff up out of the bottom of the tank. *With my retrofitted system, both
engine and polishing flow are drawn through the same suction. *I actually
can't draw a tank quite as low with the polishing system running as I can
with just the engine drawing because it sucks air down about an inch and
into the intake.

--
Roger Long

Roger I do understand that and i work in an industry where fuel
polishing is SOP because we are out in it all the time. i made the
suggestion because the redundancy to me is paramount and i never ever
trust one system when i can have a backup. I am in no way knocking
your system

Changed my mind about fuel polishing
 

On Wed, 19 Nov 2008 13:18:54 -0800 (PST), Two meter troll
wrote:

four filters. two sets paired with a y valve so you can run through
one or the other in the set. it would save you changing out filters in
bad weather (which IME is when filters clog up) or while running.

Since he has a single engine usually two switchable filters would
suffice.

Changed my mind about fuel polishing
 

On Nov 19, 8:37*pm, Wayne.B wrote:
On Wed, 19 Nov 2008 13:18:54 -0800 (PST), Two meter troll

wrote:
four filters. two sets paired with a y valve so you can run through
one or the other in the set. it would save you changing out filters in
bad weather (which IME is when filters clog up) or while running.

Since he has a single engine usually two switchable filters would
suffice.

his fuel polishing system disallows this if he wants a proper fuel
line pressure in all cases. his decision, his boat. pointing out
options was my idea.

Changed my mind about fuel polishing
 

Two meter troll wrote:

his fuel polishing system disallows this if he wants a proper fuel
line pressure in all cases. his decision, his boat. pointing out
options was my idea.

I appreciate the suggestions. However, for sake of discussion and anyone
looking at it for ideas on their sailboat:

(Schematic of my system he
http://home.roadrunner.com/~rlma/StriderFuelSystem.htm)

My system is a very tolerant, low pressure system. It runs from the main
tank quite well with gravity feed alone up to the mechanical fuel pump. The
mechanical fuel pump draws quite well from the low tank with the electric
fuel pump turned off but the vacuum is higher than I would like to subject
the pump to for long periods.

The pressure head at the mechanical pump inlet is the same when running off
the bypass as it is when gravity feeding from the main tank. If this should
be insufficient due to the secondary engine mounted filter starting to load
up or a fault in the mechanical fuel pump, I can gradually close the
isolation valve to force fuel to the engine at up to the full pressure that
the polishing pump can develop. This pump BTW does not have the pressure
cut off and regulation feature of a normal FO lift pump.

In a single tank installation with a bilge tank significantly below the
engines and fuel system, there might not be sufficient fuel pressure and
partial closing of the isolation valve might be necessary. In my case
though, I get normal fuel line pressure in all cases as well as the option
of increasing it.

It's worth repeating Rich H's brilliant idea for further redundancy:

The fuel polishing line runs to a small gravity feed tank that contains 1 -
2 hours of fuel. The line goes in the bottom of the tank from the polishing
system and exits the top on its way back to the main tank. A line runs from
this tank directly to the engine bypassing the engine driven fuel pump and
the vent has a valve on it. The fuel line could also bypass the engine
mounted fuel pump in some installations but not on mine since the injector
return line goes back to the filter instead of the tank, a Yanmar oddity.
This tank is constantly being filled, flushed, and renewed with just
filtered fuel that doesn't sit in the tank when the engine is running. If
all else fails, just open the supply and valves and a supply of clean fuel
sufficient to get the vessel out of trouble or change filters goes directly
to the engine.

In any event, I can change filters alternately on my system until I run out
of elements so I'm pretty well covered for the worst case situation. I've
also got those sails:)

--
Roger Long