Fuel Before Winter Layup

[GradyChris]

I'm sure this is a popular topic but with a lot of conflicting info I wanted to see what others were doing.
Is best practice to fill up both tanks before pulling it for the winter? Was thinking stablize the heck out of it, fill both tanks to full...ruin it a bit to cycle the stabil and additives through and then get it pulled.

I currently have 20 gals in both my main (150 gal) and aux (50 gal tank)
1998 Grady White Sailfish 272
Twin 225 Yamaha OX 66

Thoughts? Other ideas?
If ppl think that I'm better just stabilizing the 20 gals in each tank that I have now and calling it good I'm also open to that idea

 

[igblack87]

Fill them both to the top. Less room for water vapor to get in and contaminate your gas. Stabilize them both with startron or sta-bil. You'll be fine after that.

 

[SkunkBoat]

I don't think there is a right answer except that you should put in stabilizer and cross your fingers.

When I had a 20 footer with a 60gl l tank I would "nearly" fill it for winter. That was going by the idea that it reduces condensation....
(side note...that was a trailer boat...once I "filled" it in November and it leaked out the vent on a 90 degree day in April)

Now I have two 125 gl tanks. I try to leave them with 50 gls or less with the idea that I don't want to store 250 gls and risk ruining that much gas and I don't want 250 gls of 6 month old gas next spring.

That said, I have never had a problem with gas in the spring in either case.

 

[Ky Grady]

Rule of thumb in the industry is either full or close to empty. A half a tank of fuel and a warm day in the winter will create condensation in the cold tank and cold fuel. I leave mine empty during the winter and get fresh fuel in the spring. I stabilize and Ring-Free every tank, so whatever is left in the tank over the winter has stabilizer in it. Also I try and run non-ethanol fuel so that helps with the water issues too.

 

[GradyChris]

Thanks everyone
I'm thinking I'm going to stabilize the 20-25 gals that is left in both tanks and call it good.
Less chance for spoiled gas and trying to deal with that in the spring. Swap out the fuel water separators come spring time (in case of some condensation) and then fill with fresh gas and start the season

 

[seasick]

For a single tank boat, I don't fill up and haven't ever I do add Stabil , the amount based on my estimate of gas in the tank. My small boat tank tank (82 gals) has had 10-20 gals on the low end to 40 or so on the high end over the years during the winter.
The main reason I don't fill up is that I have not seen the condensation issues at my club which has maybe 90 vessels. In addition, when we do see water in the tank, it is usually due to water intrusion mostly from filler issues like bad or frequently missing o-rings.
Secondly, should you get a lot of water over the off season, come spring, you will have a lot less gas to dispose of.
Now for a boat with two tanks, I would try to run one dry and probably that would be the main if larger capacity.
I like to have enough gas in the tank to let me get a decent run in the spring without the need to gas up first. That is desirable since I gas up at a fuel dock and it doesn't see a lot o gas in the off season. I don't want to be one of the first to get a load of 'old' gas.

I do think that the condensation assumption is overblown, especially in less humid area with smaller temp shifts. I have done the math on the moisture content of the air and what could condense at typical humidity and temp swings for my area ( North east coast) It isn't a lot and to an extent having more gas in the tank can help; There is less airspace and the ethanol I have to use, will absorb about 1/2% of water by volume. So for 40 gallons of E10, the first 26 ounces or so of water would be absorbed. Winters in the northeast are typically have pretty low humidity.

As a side topic, I drain my fuel filter bowls for the Yamis, and the VST tanks for the winter. I do not drain the water separator filters since they will be change in the spring (after firing up the motors to burn off any fogging oil, etc.) In addition, if there is gunk in the tank, I would rather clog up the old filters first.

 

[drbatts]

I will try and run the tanks down as much as I can with stabilized full and then leave them for the winter. With 2 tanks one will be as close to empty as I can get it, then the other will have a little more in. I will then fill with fresh fuel in the spring. The boat typically comes out of the water thanksgiving weekend and will go back in sometime in April depending on weather and my work schedule. With the last time I add fresh gas being sometime mid October. I have been doing this using valve tech fuel, ring free and startron for the last 15+ seasons.

 

[Fishtales]

I run them down add stabilizer and fill in the spring. 20+ years with 2 GWs never an issue. You can fill and do the same. The only issue I see is then you have 100% old fuel in the tanks at the start of spring.

 

[Shannon C.]

Winterizing, what‘s that? We don’t have to worry about that on the California coast! Sorry guys, I hear ya, lived on Cape Cod for 9 years.

 

[SeanC]

Winterizing, what‘s that? We don’t have to worry about that on the California coast! Sorry guys, I hear ya, lived on Cape Cod for 9 years.

I know right. Who lives somewhere you can’t fish all year round???

 

[JerseyJarred]

Echoing what many others have said, in that year after year I try and run the tank down to roughly 20 gallons and then winterize. Fill up in the spring and off you go. Have never had any issues with this approach.

 

[Legend]

I always store with full tanks and stabilize both. I have never had an issue. Based on the variety of comments sounds like as long as you stabilize you should be fine. I have also save a lot on fuel. in most case gas prices are on the rise in the spring and its nice to have beat them at the pump at least once a year

 

[Fishtales]

I think it really does not matter as long as you treat it.

 

[langski93]

Look for an article from the recently deceased author/marine surveyor David Pascoe. I will paraphrase the title of his article but its something like, "The Myth of Water in Fuel Tanks" from condensation. He discusses the maximum amount of condensate that could be generated in a tank under perfectly ideal conditions for condensation development and finds that amount negligible and then discusses how the chance of these ideal conditions occurring is very remote. You have to do what you think is right, but give it a read and you may be looking for other sources for the water in your system. Good luck.

 

[seasick]

I agree 100% based on my experiences at my club.

 

[Doc Stressor]

The late David Pascoe was a Knower Of All Things. That's the description of a person who knows a lot about certain things and therefor assumes that he knows a lot about everything. I've been reading his reviews and opinions for many years and a lot of what he says is complete BS.

His calculation of the amount of water that could condense in a tank is an example of this. He fails to understand or at least acknowledge that a boat fuel tank is an open system. So as water condenses on the top of a tank and drops into the fuel, it is constantly replaced with air containing the same water content. Since water sinks to the bottom of the tank and is insulated from the water in the vapor phase above the fuel level, there is never an equilibrium situation. So water will accumulate continuously. There is no limit on the amount of water that can collect unless the fuel is completely replaced by water.

His understanding of heat transfer and aluminum "sweating" is also confused. The fuel in the tank heats up and cools down much slower than the aluminum or plastic tank surfaces. So each night you have a situation where the metal surface of the tank is cooler than the air in the vapor phase over the fuel.

He offers good advice, however, regarding contaminated fuel and various leak points where water can enter the tanks. But his blanket assessment that condensation is not a problem in a partially filled tank during storage can provide a false sense of security. Whether not condensation (and resulting phase separation with E10 fuel) depends on where you live. In regions with large day/night and day to day temperature swings combined with high relative humidity during the winter, it can be a serious problem and you should store your boat with a nearly full tank of stabilized fuel. This means the southeast and Pacific coastal regions. Elsewhere, low temperature and low humidity reduce the amount of water that air can hold.

When I lived in Nevada, 50-degree day to night temperature swings were not unusual. But with single-digit humidity, I could get away with a nearly empty tank. Here in Florida, I find an inch of water in the bottom of my coolers after one week if I leave them closed but uncovered on the boat.

So except for the regions I mentioned as problematic, you are OK storing your tank either almost full or nearly empty. Even if you get some condensation with an empty tank, adding fresh E10 in the springtime is like adding dry gas. The dry ethanol will absorb moisture up to around 0.4%.

 

[seasick]

I suspect we will never know for sure which rule is better: Store full or store how ever the tank level ends up at the end of the season.
I don't play the futures market. I am not going to gas up in the fall because I think gas prices will be higher next spring!

 

[everwhom]

For what it's worth, my Cape Cod marina (Nauset Marine) always fills my tanks (350 gallons) completely with stabilizer in November when I pull the boat. It's quite common for me to not fully use that gas until June or even July and I have not had any issues with stale gas.

 

[seasick]

It occurs to me that if a marina is going to stabilize a tank of gas, they would need to know how much gas is in it to calculate how much stabilizer to add. One way to know with a good deal of certainty is to fill the tank!
On my smaller boat, my fuel level reading can vary by 30 gal or 40% of the tank size. On my larger boat, I can't seem to know for sure how much gas is in there to closer than 25 gall or so or about 20% off the capacity.
So is it easier for the marina to just fill up ( and take the revenue). I wonder

 

[usmm1234]

If you use none ethanol fuel it doesn’t matter. I live in SC where humidity is super high and in the winter it 30 in the morning and 70 in the afternoon. You will absorb loads of water on a partially full tank with ethanol. I ran an outboard dealership for 12 years. We would see it all the time in the spring. The tank is breathing and the alcohol is sucking up water vapor. I use the Racors with the Clear bowl and drain on the bottom. I virtually never get water by using none ethanol.