"burn 10 or 20 gallons" ..... whats the price of fuel where youre
located???????


First draw off some fuel into a clean glass container. Hold the
glass/fuel between you and strong white light. If there is a distinct
haze (or worse) then the fuel is particulating (agglomeration/growth)
of bio-particles/slimes of cellular debris plus some oil decomposition.

If so, open the tank inspection port and look for the deposiition of
fouling on the tank walls. Just use your finger , go down through the
oil as far as you can go and feel for heavy 'slime' on the walls.
(Others have posted use of manual dip tube to test/remove the free
water - good idea.)

If the walls are found to be heavily laden with 'goo', consider to
drain ALL the oil and take it home to burn in your oil heater; then
clean the tank walls by mechanical scrubbing, etc. until all the 'goo'
is removed. Simply scrub all the goo to the bottom and then sop-up
with paper towels, etc. then burn. Once bacteria and fungi begin to
grow you have to clean the tank. DO NOT add biocide at this time as
this will simply release the cellular debris from the tank walls;
biocides are for prevention of growth. If you add biocide to a fouled
tank you will create a monster that is very difficult to clean up and
will make the cleaning much harder.

Once the the tank internals are relatively clean and most of the 'goo'
is removed; THEN, consider to 'recirculate' or 'polish' the oiil
through filters. Recirculation filtration WILL NOT remove the debris
from the tank walls if it has formed; and, will rapidly consume a lot
of expensive filters ... and will not clean the tank --- a simple
Racor filter only holds about 25-30 grams of debris. You will need to
scrub (or steam clean) the tank walls to get all the 'goo' loose if you
have developed a large accumulation. Diesel fuel tanks in boats should
be cleaned every few years anyway to prevent the release of the biofilm
and particle agglomeration from the tank walls. If you do have such
contamination and dont physically remove (scrub) the particle
deposition from the walls .... a heavy sea state WILL do it for you.
;-)

Best storage means is to - totally REMOVE the oil when the boat is not
being used for long term, especially in warm weather. If the tank is
relativelly clean and the tank is PRESSURE/VACUUM rated (rarely are)
is to put a valve on the vent line and simply CLOSE it when the boat is
not in use. Third choice is to apply a large desiccant packed
'chamber' to the vent line to remove the moisture when the tank is
'breathing' due to thermal differences of the oil and the ambient
atmosphere. The last choice is to fill the tank completely ..... but
moisture will continue to 'drive' into the oil due to chemical/physical
'equilibrium' until the oil is 'saturated' with water vapor which
eventually becomes 'free' water'.

To keep the tank clean for the longest possible interval ... only fill
the tank with the amount of oil you NEED plus a bit of 'reserve' for
emergencies. Buy your fuel from a high turn-over source such as a
depot that caters to 'watermen' ... or a truck stop; fuel from marinas
that dont 'turn over' their oil often is probably already saturated
with water.

:-)


In article .com, map
wrote:

I have not been out for about 4 months, I left my tanks half full
(mistake) and I've had problems with my diesel in the past.
My plan was to treat the current fuel with enzymes, burn 10 or 20
gallons, then fill the tanks and change filters.
Thoughts out there??