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Old 06-08-2010, 06:51   #1
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Best Fuel for a Two-Stroke

I have an ancient Tohatsu 2 stroke. In addition to the obvious stuff, oil, ethanol treatment, I was just wondering what type of fuel is best to use?
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Old 06-08-2010, 08:25   #2
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Gasoline.
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Old 06-08-2010, 08:29   #3
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Gasoline.
You beat me too it.
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Old 06-08-2010, 08:58   #4
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Gasoline.
LOL! Oops. I'm noticing more and more that you have to choose your words wisely around here. I was referring to octane. Is there a preference to Super vs. the el cheapo stuff?
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Old 06-08-2010, 09:33   #5
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The only reason to use high octane is when you have a high performance high compression engine. Your tohatsu outboard has neither. Buy the cheapest gasoline you can and mix the oil in.
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Old 06-08-2010, 09:39   #6
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Octane is less of an issue than ethanol. Ethanol enhanced fuels tend to absorb moisture out of atmosphere in a vented fuel systems.

Most outboards mid 70’s and newer were designed to live on a maximum of 10%. The problem arises when the suspended ethanol has absorbed somewhere around 2% by volume water and separates, ending up in the bottom of the fuel tank. (Google “Phase separation marine”) To be noted – this is the where the fuel pickup is. Depending on humidity can take as little as 3 weeks.

With that we now have a real good solvent that loves to eat everything from fuel lines to fiberglass, corrodes aluminum and can affect various other engine parts.

Keeping the fuel fresh and in an un-vented container is the best way to prevent it.

Hope this helps

Rick
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Old 06-08-2010, 17:05   #7
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The new "corn alcohol" mixed gasoline blends have been a major source of problems with motors not built to use the stuff. If you can find the old fashioned "straight stuff" gasoline that is what you should use. If you cannot then you will have to search for some additive or something to counteract the alcohol blended into the new ecologically correct-gasoline. If not then buy a new outboard or move to someplace that has "real" gasoline.
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Old 07-08-2010, 07:41   #8
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The only reason to use high octane is when you have a high performance high compression engine. Your tohatsu outboard has neither. Buy the cheapest gasoline you can and mix the oil in.
That's what I figured, but I did just have a dive compressor manufacturer recommend I use I high octane in that engine, so it did get me questioning.

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If you can find the old fashioned "straight stuff" gasoline that is what you should use. If you cannot then you will have to search for some additive or something to counteract the alcohol blended into the new ecologically correct-gasoline. If not then buy a new outboard or move to someplace that has "real" gasoline.
That much I knew. Been using an addative. Really, the new outboards are designed to use the ethanol gas? Where exactly should I move to? I thought it was next to impossible to find non ethanol gas these days. Maybe to an island that has their own refinery...Aruba perhaps?
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Old 07-08-2010, 20:34   #9
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The Key is to use the fuel....quickly as it doesn't do well in long term storage........

I doubt you could go to a general aviation airport and get a few gallons of avgas.......The trip would be cost prohibitive?
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Old 07-08-2010, 20:38   #10
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Go easy on the additives.....I fix a lot of carburetors and fuel sytems that have a real witches brew in them....acetone, alcohol, paint thinner, Marvel Mystery Oil, Trans fluid (it's red too), gumout, stabilizer........

I recently had a guy ask me at a Marine Store how many quarts of acetone he should put in his fuel tank......My tongue in cheek comment was...."The same ratio you put in your car" (He "got" it)
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Old 07-08-2010, 21:11   #11
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Most outboards mid 70’s and newer were designed to live on a maximum of 10%. The problem arises when the suspended ethanol has absorbed somewhere around 2% by volume water and separates, ending up in the bottom of the fuel tank. (Google “Phase separation marine”) To be noted – this is the where the fuel pickup is. Depending on humidity can take as little as 3 weeks.
I read through my manual for my 1990 Johnson 4 hp and it said it is designed for 10% ethanol. That surprised me because I know of several fishermen that have had their newer outboards fouled by the stuff.

The info about it separating and building up makes sense then since they generally have much bigger tanks and never run them dry.

Makes me feel a little better about not being able to find 100% stuff. Thanks for the info.
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Old 07-08-2010, 22:46   #12
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Offroad fuel gas isn't required to have ethanol, you may be able to get it at the jobber fuel distibutor, the same one the farms and such use, a little bit of a pain but works so much better and a lot less problems.
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Old 08-08-2010, 06:20   #13
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"Where exactly should I move to? I thought it was next to impossible to find non ethanol gas these days. Maybe to an island that has their own refinery...Aruba perhaps?"
Answer: Anywhere outside the territories of the USA. IMHO from research into the real costs of making corn alcohol gasoline shows that it is a strictly "political" product and actually costs more in "oil" consumed to make it than it replaces.
- - But anyway all the other countries of the western hemisphere use good old fashioned gasoline and 2-cycle outboards. I just loaded up my jerry cans with gasoline in Trinidad before sailing back to Grenada - the price per gallon US$0.43
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Old 08-08-2010, 08:37   #14
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Go easy on the additives.....I fix a lot of carburetors and fuel sytems that have a real witches brew in them....acetone, alcohol, paint thinner, Marvel Mystery Oil, Trans fluid (it's red too), gumout, stabilizer........
Paint thinner! All I'm adding is a little bit of ethanol treatment (the stuff you get from West, Defender, etc.)...and I mean a little bit. Maybe some Sta-bil if the fuel isn't going to be used right away. Tough to avoid unless you're putting a lot of miles on the dink.

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Offroad fuel gas isn't required to have ethanol, you may be able to get it at the jobber fuel distibutor, the same one the farms and such use, a little bit of a pain but works so much better and a lot less problems.
That's going to be a little tough to manage while cruising. Do they list those places on Active Captain?

I like osirissail's answer the best. Move out of the US. And I also agree about it being at least partially politically motivated.
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Old 08-08-2010, 08:51   #15
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. And I also agree about it being at least partially politically motivated.
You bet. The ethanol lobby is huge. In fact there is a move afoot to increase the amount from 10% to 15%.
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