Rich Hampel wrote:
Fuel polishing WILL NOT work effectively if the tank walls have thick
films of deposited sludge ...and are not cleaned FIRST.
Polishing does not remove the sludge from the walls.

In article , Gordon
wrote:

Neighbor just opened a fuel polishing business. He had a cruising
sailboat yesterday that is planning to circumnavigate and decided to
clean his tanks.
Those tanks were full of the nastiest stuff! Even big chunks of gunk.
So if you are having the slightest filter problems, I'd look at
polishing. It ain't cheap, but is good insurance.
Gordon

The big problem with gunk in your tank is not when you're putting
around in the calm bay. The problems occur when you encounter some rough
weather that stirs up all the gunk including the sludge on the sides.
My neighbors set up sucks the fuel out, filters it, and then shoots
it back into the tank at a high enough pressure to stir up the crap.
The bad one the other day had to be filtered 4 times for each tank to
clean up. And I'm sure there is some residual left on the walls but he's
a hell of a lot better off then before. Also, many tanks have small
inspection plates and baffles so I don't know a good way to clean those.
BTW, He got a call from the boatyard to come down and pump some tanks
that were leaking into a bilge. The boat is a 58 Krogen with built in
fiberglass tanks. The owners filled the tanks then had the boat hauled.
Went to dinner, came back to check on things and found diesel leaking
into the bilge from the bottom of 1 tank. Don't know if it cracked from
the lifting or ?
And I was wrong on his pricing. He gives an estimate based on $75 per
hour and he has a rough idea how long it will take. So the smallest job
is gonna cost 300 to 350 because of travel and setup. A large job won't
be much more because the actual time to filter isn't that much more.
Gordon