Fuel tank level for winter storage.

J

jhhall

New Member
Feb 19, 2008
12
Catawba Island, OH
Boat Info
36 Sovran
Engines
Cummins QSC 490HP
I had several conversations over the past few weeks about whether to store our boat with the diesel fuel tanks full or 1/4. The boat will be in heated storage. Those that say full is because it keeps the moisture out. Those that say 1/4 is to keep the weight down. Everybody says to put a biocide in. Looking for additional thoughts.
 
At the prices diesel is right now I'd consider it an investment and load as much as I could. I can't imagine that prices will stay this low for 5-6 months.
I always fill my tanks after a run anyway
 
I have only had CAT diesels for 6 years. Each year I store them with less than 1/4 tank. I never have a water build up in the Racors. I add biocide with each fill, so I don't have to add anything in the fall. Never any problems with the fuel.

My boat is stored in Canada, north of Toronto. We get plenty of cold (and snow) over the winter season.

Hope this helps.

Dave
 
I have always done 1/4 or less in heated storage with a biocide and never had a problem.
I think people filling their tanks are outside below freezing and the hot and cold creates moisture in the tanks
 
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I often wondered about the extra weight sitting on the hull from the full tanks. Just curious if anyone has given this thought. Non issue?
 
I wet slip but when I haulout they recommend that the tanks be at 1/2 or less...
 
Always store mine with full tanks here in the Northeast.
 
Gas engines
Since 2013 we have wintered our boat on land. For the first 3 years we tried to get the boat near empty when storing it. Then I read on this site you should fill it to prevent condensation. For the past 4 winters we have put it away full (300 gallons). We have not had water in fuel either way. My concern is fire when full. When we leave the boat I send the marina a note with a description of all fuel on the boat and any on the swim platform for dinghy and the location of the propane for the BBQ. Being involved in oil business with diesel fuel I would be more concerned with water due to sulfate reducing bacteria. Diesel fuel treatment will help prevent them.
 
Always full and with a fuel layup treatment.
The more air volume in the tank the more it "breathes" the atmosphere in and out and consequently the more moisture gets into the tank.
 
ttmott said:
Always full and with a fuel layup treatment.
The more air volume in the tank the more it "breathes" the atmosphere in and out and consequently the more moisture gets into the tank.
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Years ago at what seems like forever I worked on a DOD study on the storage and transport of munitions in ISO marine cargo containers. The study concluded that under the right conditions a non passive ventilated cargo container actually could become a water pump under tropical conditions. Damp air would be drawn in and converted to water via condensation during the overnight cycle, however after sunrise, air would heat up and expand out of the container faster than the moisture could be converted to water vapor. Before too long the inside of the container would become saturated.
 
JVM225 said:
I follow FrankW’s fuel treatment recommendations throughout the season and don’t do anything additional to those for winter storage.
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I treat my fuel every fill. The tanks might be full for winter layup and sometimes not. I do store the boat heated indoors, temperature swings and condensation are not a problem.
 
I'm a full tanks for winter storage type as well. It's kind of nice not needing to fuel the boat the next year until late June, sometimes even early July depending on weather :)
 
Microbes and bacteria can live on the sides and tops of tanks as well as in the fuel not treated with a biocide. So if your tank is less than full all areas inside of the tank that are not submersed in fuel treated with a biocide are subject to microbe and bacterial growth.
I treat a partial tank with biocide sufficient to treat the tank as if it is full then top off the fuel to full.
 
I use star tron by starbrite biocide every fueling and Diesel Kleen cetane boost with slick diesel every other. Always layup in water or not with 1/4 tanks, never had a condensation issue. Racors always come clean no water or alege. Gas/Diesel weighs 6lbs/gal. x 240 x 2 is a lot of weight if you out of the water. The hull isn't use to supporting that much weight sitting on blocks on the keel. It's designed for having every sq. inch of the bottom having water pressure against it to help support that weight. So the less weight the better in my book.
 
Ours is outside under shrink wrap and we see very cold temps. Always have the tanks topped up and the fuel treated with a shock level of biocide. Only other treatment for the winter is the addition of fuel conditioner. We have not had any water issues thus far. Have thought of the weight issue but haven't heard of any boat being damaged as a result of a full fuel load on blocks ... I've always assumed that designers take this into account since every boat will be out of the water and on blocks at some point.
 
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