Stored Fuel Longevity

[svHyLyte]

This past June we made a cruise to Key West and carried along our inflatable dinghy and outboard. Upon returning we had roughly 5 gallons of gasoline remaining, mixed with TC lube oil at a ratio of 50:1. As nothing else is now available here, the gasoline was/is a 10% mix of ethanol. The question is, how long this fuel can be retained/stored. At the suggestion of an acquaintance I recently purchased some “Startron” gasoline fuel additive that supposedly counters the effects of Ethanol but have not added it to the fuel as yet. I’m wondering whether I can reasonably keep the fuel for a few more weeks or months or whether it would be wiser to simply donate it to our grounds keeper and buy fresh sometime later.

Any knowledgable opinions?

s/v HyLyte

[Sunspot Baby]

I vote donate and replace.

There are some good threads on the effects of using ethanol in out boards on this forum. Do a quick search.

George

[SilentOption]

I just had my carb rebuilt because my obm sat unused at least 9 months.
The fuel was ethanol mixed although any fuel may have gone bad in that period of time. When the motor didn't start I checked everything and finally got to the tank. It smelled like paint thinner.
If you plan to let your obm sit long, drain the carb no matter what additive you are putting the fuel.

[cabo_sailor]

I'd probably add a bit, like a half gallon to gallon at a time, to my truck fuel tank. Diluting that much oil mix in 20-25 gallons of regular fuel shouldn't hurt anything.

[s/v 'Faith']

Many years ago I pulled wrenches in a motorcycle shop. We prepped and delivered the outboards, but we mainly sold and serviced motorcycles and ATV's. Our tech rep used to give us 'classes' on different problems with various aspects of service.

One of his presentations was on the rate at which mixed fuel broke down. Gasoline is fairly stable as mixed by the producer, but 2 stroke oils not only begin break down in as little as 30 days, they also can promote the break down of the gasoline.

If you pour old pre-mixed gas into a clear container you will notice that the color changes as it ages. The problem is that you have no way of telling how much the gas you are storing has broken down.

All that said, I have burnt old 2 stroke in my mower for years. It rarely even causes the plug to foul.

[Chief Engineer]

I have rebuilt/cleaned 6 carburetors on customers outboards this year.

I have three more in line.

Normally I don't "do" outboards but they all have had the same problem.

Lightly used dinghys+aging fuel=carburetor problems.

My advice is when you are getting ready to stow the dinghy. Start the engine and disconnect the fuel line to run the fuel out of the carb(s)

[svHyLyte]

Thanks for the observations. In past we've kept fuel for a full summer season with no problems but this business of adding ethenol is a new twist and I've read that the stuff attracts a lot of water. Supposedly the Startron will counter that but I have misgivings about running the stuff through a relatively new $2,000+ (USD) outboard. For the sake of $30, I guess we'll run some of it in the mower and give the rest to the groundsmen.

Funny. We have a near 50 year old lawn mower and a 57 year old chin saw--both with noisy little Briggs and Stratton 2 cycle engines that get virtually no attention and seem to run on just about anything (I actually put kerosene in the Chainsaw by accident once and it still worked). They just keep going and going--Of course I do change the spark plugs every 7-8 years. Yet we have to baby outboards.

N'any case--thanks for the sugggestions.

s/v HyLyte

[Gator81]

I use SeaFoam fuel treatment in the gasoline fuel I store over winter in various engines, both 4 and 2 stroke, with no problems. [Caveat - none of these are outboard motors, tho I can't imagine any difference.] For stabilizing fuel, I notice the manufacturer recommends a mix rate of 2 to 4 times as much for 2-stroke fuel as for 4-stroke fuel.

My procedure is to mix the additive with the fuel as recommended, run the engine long enough to be sure the carbs are full of treated fuel, and then top the tank up to eliminate air (and the moisture it carries). Six months or more later, and they start right up.

If you feel the need to fog the internals, you can turn the engine over a few times with the ignition disconnected as a last step.

Is there any reason this wouldn't work with the ethanol/gasoline mix?