Boat Storage - Full Gas Tank vs Less Than Full

[pdhj1990]

I've been participating in a thread on another forum that addresses boat storage:

http://www.centurioncrew.com/storing-boat-t3922.html

The issue is whether to store the boat with a full tank of gas and stabil or a near empty tank with stabil.

Apparently, Ethanol blended gas has a poor shelf life and it attracts water. Neither is good for boat motors.

How do you all store your boats - Full tank or nearly empty? Also, what are your thoughts as respects to summarizing your boats and the fuel?

Furthermore, our winters in Texas are rather short - maybe 3 to 4 months max. Does this affect anyone’s opinion?

Paul

[zad0030]

Full tank with Marine Stabil....

Stabil I think claims to preserve gas for 6 months.

The best procedure is to fill it full, add stabil, and then run it a little bit, like for winterization purposes. This will allow the stabil to go through the fuel system and also lowers the level in the tank enough so that it wont expand out.

[whitlock87]

X-2
on what ZAD said

[chpthril]

Just dont fill the tank too full, as the temps warm, the fuel will expand and purge out the vent. Sta-Bil makes a storage treatment for ethanol fuel, I think it's the green.

Ethanol will have no more harm on your 06 fuel system, as it would a new car today. Ethanol is not new, and the manufacturers of the rubber and plastics used in late model fuel system have blended them (fuel systems) to tolerate ethanol. As far as hurting the actual engine, this is an ol moekaniks tail.

[chpthril]

Pdhj,

Saw you latest post over on the CCC, no need add an octane booster! It's nothing more then snake oil If your engine was run after the stabilizer was added, you will be fine come March when you break her back out.

[robert theisen]

the marine stabil is blue and is available at most marinas.

[bfrank]

I always filled it, until this year!! Had problems with Ethanol sitting too long. What I did was run it below half and added marine stabil. So next year I can fill it up and have at least more than half in fresh gas!!

For the past two years my first runs out were terrible with gas problems. You would be runnung and it would just dog out! Changed everything fron fuel filters to plugs, wires, cap, all to have the same problem. Ethanol gas sucks and seems to be getting worse.

I ski with a Mercury engineer he gave me a gas tester to see the percentage of alcohol persent in the gas. Most of the stations are between 5% to 10%.

[talltigeguy]

I saw your thread also on Malibucrew.

I think you have about 12 different approaches now and the reason that happens is because no one really knows, IMHO. If there were absolutely one right way, then I think we would all do it that way.

Methinks you worry too much on this one.

[pdhj1990]

Talltigeguy,

You're probably right - no one really knows. However, I do find the divergence of opinion pretty interesting.

Thanks.

Paul

[Iwndr]

I always filled it, until this year!! Had problems with Ethanol sitting too long. What I did was run it below half and added marine stabil. So next year I can fill it up and have at least more than half in fresh gas!!

For the past two years my first runs out were terrible with gas problems. You would be runnung and it would just dog out! Changed everything fron fuel filters to plugs, wires, cap, all to have the same problem. Ethanol gas sucks and seems to be getting worse.

I ski with a Mercury engineer he gave me a gas tester to see the percentage of alcohol persent in the gas. Most of the stations are between 5% to 10%.

X2, 1/2 tank and run it with Stabil before putting it up. Top it off in spring and enjoy

[IDBoating]

The lower the amount of fuel in the tank over the winter, the greater the amount of air. Air contains water (humidity), and that water will condense out on the walls of the fuel tank as the temperature cycles during storage. You're effectively adding water to your fuel.

Personally, I do the following:

* Drive the tank down close to empty
* Winterize the engine
* Dump the proper amount of StaBil in the tank (before filling, so you get a better distribution of the StaBil in the fuel)
* Fill the fuel tank to about 95% of capacity with premium (highest available octane) NON-ETHANOL gasoline

This approach minimizes airspace/moisture, eliminates ethanol storage concerns, and improves the octane left in the fuel when you start things up next season. You can alter it to optimize for any one of those things (say, leave the tank mostly empty so you have higher octane in the Spring from fresher fuel) but doing so will suboptimize the others (say, increase the amount of water in the tank).

BTW, non-ethanol fuel is generally available if you look for it. Most marinas have non-ethanol fuel, for example. Call the local office of a couple of major gasoline companies and ask them where they deliver non-ethanol fuel in your area. In my case, the premium gasoline delivered to the nearest gas station to my lake place happens to be 0% ethanol. Lucky me!

[chpthril]

Fill the fuel tank to about 95% of capacity with premium (highest available octane) NON-ETHANOL gasoline

NNNNOOOOOOOOOOOOOOOOO!

As fuel ages, it become less volatile (harder to ignite and less BTU's p/gallon), so why would would want to store with fuel that's half way there

The reason the higher octane fuel is refined for high compression engines and prevents spark-knock (unwanted ignition) is because it takes more heat to ignite. As it ages and begins to spoil, it takes even more heat to ignite.

[IDBoating]

The reason the higher octane fuel is refined for high compression engines and prevents spark-knock (unwanted ignition) is because it takes more heat to ignite. As it ages and begins to spoil, it takes even more heat to ignite.

Yeah, that's a pretty good point. I'll yield on the octane.

However, around here only premium is non-ethanol. I'm committed to avoiding ethanol in my marine engines as long as possible. So I'll continue to live with "excess" octane to keep the ethanol out of my tanks and engines. Other localities may have different ethanol mixing rules, which is why I suggested folks call their local delivery companies to be certain.

[IDBoating]

This has been bugging me for a long time. The octane vs. stale fuel thing just didn't "feel" right to me. Today I finally had a chance to research it a bit more.

The RON rating (commonly but, strictly speaking, erroneously referred to as "octane") refers to the fuel's tendency to burn in a controlled manner, as opposed to exploding. Basically it's a measurement of flame wall propagation speed. As pressures increase, the likelihood of detonation increases but the effect can be offset by additives which increase the RON rating.

The RON rating is entirely separate from the fuel's energy content. Therefore, winterizing with a full tank of higher-RON-rating fuel does NOT mean you're "halfway there" with respect to stale fuel. The fuel's energy content degrades entirely separate from its RON rating.

One rating (RON) has to do with flame wall propagation. The other rating (heat content) has to do with available chemical energy. "Stale" fuel is slang for a degradation of the latter. A higher RON ("octane") rating does not indicate less energy content.

Hope this helps!

[Ewok]

I saw your thread also on Malibucrew.

I think you have about 12 different approaches now and the reason that happens is because no one really knows, IMHO. If there were absolutely one right way, then I think we would all do it that way.

Methinks you worry too much on this one.

I think the biggest aspect of the ethanol debate is the wide variety in the ages of boats and their fuel systems, carb vs EFI, and the various storage times from different parts of the country (6-9 months up north vs 1-2 months down south). That is why you have many different opinions (some correct, some just because its always been that way) on the proper fuel treatment for storage.

To get the best advice we just need to follow the boats manual unless it pre-dates the ethanol fuel mixture. However, using marine stabil is always a good idea, and leaving room in the tank is a good idea if your storage area is going to warm up before you take the boat out again. If you think you got water in the tank because it was not full then you can add a little HEET, water absorbing additive, to the spring gas. If you have a carb engine, I would expect that varnished gas will clog it sooner than later but carb cleaner and a rebuild every 5 years or so kept me in the clear on my old boat.