Fuel Tank Winter Storage

[Firenailer]

It's still early - but it's getting near time to start thinking about the end of the season here in the Northeast. I've paid my deposit on my winter spot and the Marina has sent out its end of season and close date letter.
What is the general consensus from our learned members on Winter Fuel Level during storage? In the old days we were told to store it full to the brim to prevent condensation from forming. With today's Plastic tanks and all of the Ethanol fuel separation issues we've heard about - what is the proper or preferred method of storage - Full or Low? :hmm

 

[eppem]

I have two tanks, the front / main tank we use all the time. The back / "reserve" tank we use for offshore trips and longer hauls. I will run 20-40 gallons thru the back tank during the season to keep the tank in use.

Why all that history? Because when we haul in December we fill the front tank an add stabil, the back tank we leave as it, it probably has 10 gallons sloshing around in it? I toss in any extra stabil / winterizing mix and we are good to go. Knock on wood, 11 seasons with no fuel issues. Now, we are back in the water in March, so our off season is pretty short. But to answer your question, fill er up or drain it down.

EPPE

 

[Finest Kind]

IMO, and the way I do it....
Since it is a known fact that Ethanol gas does NOT store well long-term and is prone to phase separation, why take a chance with full tanks?

Run your tanks as close to empty as you can get them. Dump in double the amount of Startron and Stabil as recommended and put your boat to sleep for the off-season.
Add fresh gas upon re-launching and enjoy the new season.

 

[Firenailer]

That's the million dollar question Len! Old days Full tank was the norm. With this ethanol and plastic tanks I'm leaning towards the empty side and heavy stabilizer myself. Asking around the marina gets as many varied answers as you'd expect.....

 

[DennisG01]

I still subscribe to either full or empty, never in between. Condensation (physics) hasn't changed. Although I believe in the full or empty process, I have NEVER emptied my tanks (I rarely even empty the lawnmower, snow blower, weedwacker, chainsaw, etc). But I do use Startron religiously in everything. This goes for about 5 boats I've personally owned since ethanol came onto the scene, along with another dozen and a half or so that are either family member's or boats that I service as a small part-time job. Zero fuel problems. Some boats have occasionally gone over a year without new gas. If you can empty it and it's not too inconvenient, go for it. But with bigger tanks, it's not usually easy to do. Dose it, fill 'er up, be done with it.

 

[Ky Grady]

This will be my first winter with my current boat. I'll probably store the auxiliary full and treated and the main empty and treated also for what remains. Years past only had a single tank and always stored it full and treated with no issues. StaBil and RingFree is my usual additive.

 

[Bumpye]

Based on my boat shop's advice. Leave them almost full to allow for expansion in the spring. Fuel stabilizer and you'll be OK.

 

[artodea]

I'm in the empty tank camp - or as close to empty as I can get. I fill in the spring and go fishing.

Here's a link to thoughts on condensation:
http://www.yachtsurvey.com/myth_of_condensation_in_fuel_tanks.htm

 

[seasick]

I'm in the empty tank camp - or as close to empty as I can get. I fill in the spring and go fishing.

Here's a link to thoughts on condensation:
http://www.yachtsurvey.com/myth_of_condensation_in_fuel_tanks.htm

Me too. As close to empty ( 10-15 gals maybe). I add Stabil in the storage dosage and have had no issues in 11 years. If for whatever reason, your gas gets spoiled, you will have a lot less gas to get rid of if the tank is close to empty.
I do not drain the tank completely; that is a pain to do and in my mind doesn't add a lot of insurance.
What will add a ton of protection is to check and replace as needed your fuel fill o-rings. 99% of the problems I see at my club dealing with water in the gas are due to leaky/missing fuel cap o-rings. I have not seen a case of phase separation in quite some time.
I have seen boats stored for 3 years on land that still have usable gas. If it looks like gas and smells like gas, it will probably be usable. Bad gas often smells really bad!

 

[Hammertime]

Drain your tank as much as possible, Then winterize the motor. If you can get a hold of ethanol free gasoline, do so and run the fuel through your filters and VST, add star tron and you are set for the spring with no worries..

 

[seasick]

Drain your tank as much as possible, Then winterize the motor. If you can get a hold of ethanol free gasoline, do so and run the fuel through your filters and VST, add star tron and you are set for the spring with no worries..

I guess there are many options. I didn't mention that although I don't run the tank dry, I do take a short trip after adding the Stabil to make sure it gets into all the fuel system components and gets mixed up in the tank. After hauling a nd all the winterizing thingg, I empty the VST tank and drain the engine mounted clear fuel filter bowl.

 

[Fishtales]

I agree with Len. Run them down and stabilize for the winter. Fill up in the spring and off you go. I've done this 20 years now and never an issue. This is what my dealer does with 100s of boats and he says never an issue.

 

[Firenailer]

Ok men, thanks for the replies! I'll run her down as far as I can before bringing her back up to CT for her winter nap.

 

[JeffN]

I have tried various programs with my winter fuel storage. Pretty much settled on storing the tank with whatever is left in it after my last fill up and usage. Sometimes it is mostly full, near empty or anywhere in between. I stabilize before I run it the last time and then just put her away for the winter. My lay up lasts 5 months or so and no issues so far. My boat has an I/O and people say I/Os are somewhat more resistant to fuel contamination than OB, don't know if that is true. I have asked at the yard and they tell me that they just stabilize what is in the tanks and really don't have problems YMMV.

 

[seasick]

I have tried various programs with my winter fuel storage. Pretty much settled on storing the tank with whatever is left in it after my last fill up and usage. Sometimes it is mostly full, near empty or anywhere in between. I stabilize before I run it the last time and then just put her away for the winter. My lay up lasts 5 months or so and no issues so far. My boat has an I/O and people say I/Os are somewhat more resistant to fuel contamination than OB, don't know if that is true. I have asked at the yard and they tell me that they just stabilize what is in the tanks and really don't have problems YMMV.

I don't think I/O vs outboard makes much difference as far as issues in the gas tank go.
There may be different concerns about those motor options with regards to fuel issues in the engines them selves and more importantly in carbed motors as opposed to injected motors.
I see many more fuel issues in carbed motors after storage primarily to gummy deposits that form in the fuel bowls and clog the needle valves and jets. For whatever reason, it seems that carbed motors have more problems even when the gas is treated and run through the motor. That may have something to do with the fact that many carbs have a vented bowl whereas injected motors have in effect a sealed fuel system.

I have several older boaters in my club that will never store their carbed motors with empty fuel bowls since they believe that gaskets can dry out and shrink. Older model motors seem to be more of an issue. I know folks who fill their carbs with oil (not fogging fluid) during storage and drain it out in the new season before priming with gas.

To me it boils down to this: It is a pain to fully drain a builtin gas tank and you can create more problems than you might avoid.
I would rather have to toss out 20 gals of bad gas instead of 100 or more should the gas go bad for whatever reason during storage. So for me, run low, add stabilizer, shake it up and wrap it up

 

[Doc Stressor]

Here's the physics behind the recommendations for full tank/empty tank recommendations:

1. With a full tank (and I mean really full), there is little space for the exchange of moisture laden air between the tank and external atmosphere. This exchange is largely the result of expansion and contraction of the fuel/air space during temperature changes. With a full tank, very little moisture will accumulate during winter storage.

2. With an empty tank, moisture will accumulate except if the boat is stored in a low humidity (mountain or desert) environment. If you have fuel containing ethanol, phase separation will take place. But when you fill the tank back up in the springtime with fresh ethanol containing fuel, that water will be absorbed back into the fuel (up to a point). This does not work in high temperature, high humidity areas like Florida. Here, the amount of water that will accumulate in an empty tank will be more than can be absorbed by the fresh fuel. But in most of the country, this method works fine. Cold air contains much less moisture than warm air.

The point is to never leave a tank partially filled over the winter. You might be OK with non-ethanol fuel where the water separating filters will remove any water that might accumulate. But you will likely have phase separation if you have ethanol containing fuel in there.

I've been using the full tank method with the recommended storage dose of StaBil since the 1970's and I've never had a problem.

 

[seasick]

Here's the physics behind the recommendations for full tank/empty tank recommendations:

1. With a full tank (and I mean really full), there is little space for the exchange of moisture laden air between the tank and external atmosphere. This exchange is largely the result of expansion and contraction of the fuel/air space during temperature changes. With a full tank, very little moisture will accumulate during winter storage.

2. With an empty tank, moisture will accumulate except if the boat is stored in a low humidity (mountain or desert) environment. If you have fuel containing ethanol, phase separation will take place. But when you fill the tank back up in the springtime with fresh ethanol containing fuel, that water will be absorbed back into the fuel (up to a point). This does not work in high temperature, high humidity areas like Florida. Here, the amount of water that will accumulate in an empty tank will be more than can be absorbed by the fresh fuel. But in most of the country, this method works fine. Cold air contains much less moisture than warm air.

The point is to never leave a tank partially filled over the winter. You might be OK with non-ethanol fuel where the water separating filters will remove any water that might accumulate. But you will likely have phase separation if you have ethanol containing fuel in there.

I've been using the full tank method with the recommended storage dose of StaBil since the 1970's and I've never had a problem.

I can see how in southern more tropical climates, condensation can be an issue but here in the northeast, I haven't had or seen a lot of problems with water due to condensation. In my current boat, that is 11+ years and I always store with a third to a quarter of a tank.

Being a retired engineer, I actually went through the calculations of how much water would condense in my tank for extreme temperature swings and I mean extreme swings. To be fair, it can be 40 degrees outside but a shrink wrapped boat in the sun can have much higher temps under the cover. Nevertheless, I couldn't see a really strong case for a water issue.
Their are a lot of opinions on the topic and they come up every fall. It would be very informative to see a real scientific test say two or three identical boats, one with an empty tank, one a quarter full and the third full, shrink wrapped and stored for a winter or off season followed by a lab analysis of the tank contents at the end of the test. Who knows, I might be surprised.

 

[mheltunen]

Regarding fuel level for winter/extended storage the rules have changed a bit since ethanol was introduced. Myself (until I sold my boat) I used only ethanol free fuel which is still available in Michigan. That allowed me to fill the tank full to prevent any condensation from building in the tank. When ethanol was introduced on the market it caused huge headaches for boaters. Ethanol fuel is hygroscopic and absorbs water 50 times more than conventional non alcohol gasoline. So to sum up my experience, if you run ethanol in your vessel store with as little as possible in the tank. In turn if only non ethanol fuel is used then top the tank off to full for long term storage.

 

[seasick]

Regarding fuel level for winter/extended storage the rules have changed a bit since ethanol was introduced. Myself (until I sold my boat) I used only ethanol free fuel which is still available in Michigan. That allowed me to fill the tank full to prevent any condensation from building in the tank. When ethanol was introduced on the market it caused huge headaches for boaters. Ethanol fuel is hygroscopic and absorbs water 50 times more than conventional non alcohol gasoline. So to sum up my experience, if you run ethanol in your vessel store with as little as possible in the tank. In turn if only non ethanol fuel is used then top the tank off to full for long term storage.

I think there are some valid points and some not so valid points in your theory.
Yes ethanol is hygroscopic and will to an extent absorb moisture. However, if water condenses on the tank walls, It has to go somewhere. if it runs down the sides of the tank or drips off the top it will endup at the bottom of the tank beneath gas. Ethanol on the other hand will adsorb a certain amount just like 'dry gas' did in the past. Dry gas was mostly alcohol. So in some cases, ethanol gas has an advantage. So for a 50 gallons of fuel, the first quart of water will be absorbed. For non ethanol, a quart of water will sit on the bottom. That water only builds up over time when non ethanol gas is added whereas, when new ethanol is added some of that water gets absorbed and burnt off during normal operation.
I have seen all the early issues when E10 was mandated in my area but honestly, I really don't see a lot of issues these days.

 

[Fishtales]

Regarding fuel level for winter/extended storage the rules have changed a bit since ethanol was introduced. Myself (until I sold my boat) I used only ethanol free fuel which is still available in Michigan. That allowed me to fill the tank full to prevent any condensation from building in the tank. When ethanol was introduced on the market it caused huge headaches for boaters. Ethanol fuel is hygroscopic and absorbs water 50 times more than conventional non alcohol gasoline. So to sum up my experience, if you run ethanol in your vessel store with as little as possible in the tank. In turn if only non ethanol fuel is used then top the tank off to full for long term storage.

All I know is 20+ years with running it down, treating it and filling in the spring. Never one issue with fuel. If it were to go bad, 90% of the fuel in there is new/good so you likely can ride through it. Fill the boat and it goes bad, you're pumping it all out. Just sayn...