What to do with diesel in the tank over Winter?

[FruiVita]

I have an S2 11.0 sailboat with a 70-gal aluminum fuel tank. I keep the boat near Annapolis and leave it in the water during the Winter. Winters are cold but not harsh, and we do Winterize. My question pertains to what to do with the diesel that's in the tank. There are roughly 50 gallons, of which about 15% is older than this past season. (I am a newbie sailor who bought the boat in January 2013 and only added 12 gallons all year.) So, the fuel is of unknown age but mostly older than a year. It has been treated with a high-grade (well....high cost anyway) fuel additive. I have noticed that when I change my fuel filters (I use 10 microns) the fuel is black and there's a bit of sludge in the bottom of the old Racor 200. This does not seem right but the engine seems to be running fine on the treated, filtered fuel.

My questions are:
1. Should I top off the tank, treat it again, and just crank it up again in the Spring?
2. Should I 'polish' the fuel and somehow clean the tank and first stage lines? If so, is this best left until Spring, since the engine will not likely be operated after Thanksgiving and various flora and fauna could grow in there over the Winter?
3. Should I remove the fuel from the tank? This seems counter to everything I've read about keeping tanks full to avoid condensation, but the tank seems full of questionable fuel.
4. Is there a 4th approach I should take?

Welcoming the wisdom and experience of my fellow CFers...

[delmarrey]

I use to just polish mine every spring. But I also kept the inside of the boat warmer then the outside, which kept the moisture factor down.


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[Capt Phil]

If I were you, I'd wait until spring, polish the fuel and lines, change out the filters and keep the tank full through the next few winters. Clean, full tanks tend not get dirty as quickly as most sparingly used systems.
If you can, get your boat out into a seaway and stir things up being prepared to change out the filters at the first signs of surge or fuel problems.
The only sure way to maintain clean fuel is to start with clean tankds and keep them that way. Additives will work to a point but prudent clean fuel management constantly is the best solution. Phil

[Vasco]

Just treat it (I use Startron). I would not even bother to top up the tank. Maybe have it polished in the spring. Then you'll know the fuel is fine.

[Cheechako]

Originally Posted by Capt Phil

If I were you, I'd wait until spring, polish the fuel and lines, change out the filters and keep the tank full through the next few winters. Clean, full tanks tend not get dirty as quickly as most sparingly used systems.
If you can, get your boat out into a seaway and stir things up being prepared to change out the filters at the first signs of surge or fuel problems.
The only sure way to maintain clean fuel is to start with clean tankds and keep them that way. Additives will work to a point but prudent clean fuel management constantly is the best solution. Phil

[sailorboy1]

I top mine off and treat it on lay up storage.

I'm seriously considering installing a vent filter to keep the moisture out of the tank.

[rw58ph]

I would add an additive that absorbs water back into the fuel and keeps from separating. I use diesel treatment 911, red container, sold at most auto stores. Try to use/turn the fuel at least once every year as the new slow sulfur and ultra low sulfur does not last long. Most off road/marinas is low sulfur and most on road is ultra low sulfur with maybe small % of bio. Anyway you should be OK through the winter. Make sure you use/turn it next summer.

Also you should know what kind of diesel your marina is pumping, off road - low sulfur, utra low sulfur, % Bio?

We hold 1,200 gallons, but usually carry 400 to 500 gallons as that is what we can turn/use in a year, add addives each winter and polish the fuel year around. Best time to polish is during a winter storm when the boat is rocking and rolling as it stirs up the grud.

[eschlanser]

What do you all mean by "polish the fuel"?

[delmarrey]

Originally Posted by eschlanser

What do you all mean by "polish the fuel"?

Filter it for water and crud.

[DeepFrz]

I would polish it to remove any water that may be lying in the bottom of the tank. This water could cause your tank to corrode. The cleaner you can leave the fuel/tank over the winter the better off you will be, IMHO.

[rw58ph]

Originally Posted by eschlanser

What do you all mean by "polish the fuel"?

Using an electric fuel pump, pumping diesel though the external primary fuel filters to clean/polish. Also can be used to transfer fuel from one tank to another. Most boats with large tanks have a fuel polishing system built into the fuel system.


Might be more of a power boat thing?

[eschlanser]

Originally Posted by delmarrey

Filter it for water and crud.

So, you pump it out, filter, then put it back in the tank? Or what? I'm a new boater and this is a new term to me. I have had a diesel pick up truck for many years and never heard about poishing the fuel.

[rw58ph]

Originally Posted by eschlanser

So, you pump it out, filter, then put it back in the tank? Or what? I'm a new boater and this is a new term to me. I have had a diesel pick up truck for many years and never heard about poishing the fuel.

Yes, you pump it out, filter and pump it back into the tank. Probable never heard of it as most vehicle have small tanks and the diesel is used/turned frequently. Actually most diesel engine will polish/clean the fuel as they draw more fuel than they use, so the excess is return back to the tank.

Our main 671 will draw about 60 gallons per hour but uses max of 8 gallons so about 50 gallon is filter/polished/clean back to the tank. However, boats tend to have big tanks and many boats sit for months at a time, so the fuel becomes a concern. Not much to polishing systme if you already have external primary filters. A DC electric fuel pumps, manifold made of pipe and valves, and some hose. Cost maybe 100 bucks.

So you now say, well I will just run my diesel engine and polish the fuel. However, running an engine with no load is not recommended for long periods of time. So if a boat has large tanks, not used much, the best way is to use an electric pump.

[DeepFrz]

I doubt you could polish your shoes with the amount of diesel returned from the size engine we are talking about. Or any marine engine for that matter.

[Chenega]

Polish it and transfer to your furnace at home. Clean out the tank and re fill... I want to know I have good fuel in the boat. My house just has to stand there but the boat is my ride home.