"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

"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

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. :-)

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

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)

"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

"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.

"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

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

"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