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Old 16-12-2013, 05:03   #1
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Outboard fuel deteriorating how long

OK so here is the question, how long will you keep your unused outboard petrol before changing it for fresh petrol. The reason I ask is a few weeks ago my three year old Honda 20 HP stated to run roughly at idle in fact it would not idle at all, it started fine, ran fine but would not idle. The local guru's suggested it may be the fuel is to old, they advised after three weeks I should really change it, another advised about three months yet another advised should be OK up to around 14 months. They felt the octane level reduces quickly so better to buy the highest one can buy.
Today I changed the fuel ran the engine no problem the idle still cutting out so I just would the idle screw in a bit now it seems fine. But I'm not sure if it was the fuel ore not. So how long before you feel you should change your unused fuel for fresh fuel.
Peter
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Old 16-12-2013, 05:06   #2
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When I buy dink fuel (at home not cruising) I'll only buy a gallon , use a pint, and mix the rest into the law mower. Within a month.
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Old 16-12-2013, 05:46   #3
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Re: Outboard fuel deteriorating how long

I think in Oz you're gasoline (petrol) supply doesn't have a percentage of ethanol included?

Back when the U.S. was like that, gas seemed to last forever if kept in a completely sealed container and stored in friendly temperatures... Less long, if the tank was vented. Here, with ethanol now, about a month (but I usually recycle after 3 weeks).

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Old 16-12-2013, 05:49   #4
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Re: Outboard fuel deteriorating how long

I think it depends many things, temp,quality to start with, container,agitation, the good stuff in the fuel evaporates away pretty fast these day I have seen it go bad any where from 3 months to a year at the very most. Stabil does help
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Old 16-12-2013, 06:09   #5
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Re: Outboard fuel deteriorating how long

I only buy ethanol-free gas for the outboard (5 hp 2-stroke) and it seems to stay viable for up to 4 months, But I religiously burn off any unused gas in my truck at the end of the boating season, and start with fresh gas in the spring.

If I had to use gas with ethanol in our outboard, I'd for sure use stabiliser in it; even so I'd aim to be using it all in a month, and having mainly fresh gas if going out for an extended period.

I've had very good luck with seafoam for helping engines that are running roughly due to clogs. If that doesn't work, you'll probably need to dismantle the carb and check for clogged jets.
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Old 16-12-2013, 07:16   #6
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Re: Outboard fuel deteriorating how long

Even with ethanol, it will keep 6 months easily (based on lab and field testing). What is vital is to exclude water and provide corrosion protection.

Water. There are vent filters available that reduce water gain and reduce gasoline and ethanol loss, nearly like having a sealed tank. On small engines, close the vent when not actually in use.

Corrosion. There are a number of additives that stop alchohol and salt induced aluminum corrosion, the most common cause of plugged jets. Seafoam is a good one, as are Merc Stor-n-Start and Biobor EB.

---

I have not bought gas in small quantities, bough ET free, or run a carb out in 25 years, and my last clogged jet was on a boat I had just bought. The right additive, close the vent if there is one, use a vent filter if there is not, keep the tank full to minimize breathing and oxygen exchange, and use the boat. No problems.
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Old 16-12-2013, 08:05   #7
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1 month for untreated, six months for treated with stabil.

Some things (like small four strokes) seem much less tolerant than others.
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Old 16-12-2013, 08:12   #8
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Re: Outboard fuel deteriorating how long

Back when I was pulling wrenches in the Yamaha / Honda motorcycle shop, the Yamaha tech rep was saying 90 days max for pre-mixed fuel.
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Old 16-12-2013, 08:24   #9
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Re: Outboard fuel deteriorating how long

I've decided to avoid all these problems with gasoline and switched to propane. I can store the fuel forever and the carb never gums up.
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Old 16-12-2013, 08:33   #10
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I think people that have life expectancies for the fuel should include the climates the fuel is stored in. I would think the humidity and temperatures could make a significant difference in bio contamination. Also, what did it take to convert to propane? I assume it must be for 4 stroke motors?
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Old 16-12-2013, 08:49   #11
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Re: Outboard fuel deteriorating how long

Ditto, HopCar! Propane is probably more available internationally than fresh gasoline, and probably doesn't have chunks of rust, dirt and water sitting in the bottom of the tank. I'm getting rid of all my old outboards and going with a 5 and a 15 HP Lehr. The West Coast rep was visiting the San Diego West Marine last weekend and gave me a bunch of flyers for the new 15. He said the 15 can be ordered with a starter/charger for those of us who want to have a battery aboard for electronics. This is a game-changer.
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Old 16-12-2013, 09:01   #12
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Re: Outboard fuel deteriorating how long

I do something that solves the problem for me that is probably not common but is useful to know.

I have found that aviation fuel works great (100 low lead) is actually leaded gas but never has ethanol and has stabilizer in it (because airplanes often sit in the hot sun for long periods and the gas has to remain good). It is at least $1.00/ gal more expensive.

Anybody can buy it and it is the most dependable gas I have found.

Slightly more polluting but used is small amounts not a big deal.

Just and idea.
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Old 16-12-2013, 09:21   #13
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Re: Outboard fuel deteriorating how long

Quote:
Originally Posted by taildragerdrive View Post
I do something that solves the problem for me that is probably not common but is useful to know.

I have found that aviation fuel works great (100 low lead) is actually leaded gas but never has ethanol and has stabilizer in it (because airplanes often sit in the hot sun for long periods and the gas has to remain good). It is at least $1.00/ gal more expensive.

Anybody can buy it and it is the most dependable gas I have found.

Slightly more polluting but used is small amounts not a big deal.

Just and idea.
You forgot to mention how "yummy" Av gas smells when you burn it!
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Old 16-12-2013, 09:41   #14
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Re: Outboard fuel deteriorating how long

Taildragerdrive...looks like a 170 you have there, is it an A or B?
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Old 16-12-2013, 09:43   #15
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Re: Outboard fuel deteriorating how long

Quote:
mix the rest into the law mower.
arnt they illegal!, have you much call for such a device

dave
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