# Gas question:



## BananaTom (Feb 16, 2008)

This is a Buddy of Mine's post on a forum with less members, and few replies.
So I am helping her by posting here: Thanks for your help.


*I just made the hour-long trek to buy ethanol-free gas, all ten gallons of it at a time, and decided that was a stinky chore I would like to minimize.

So: anybody know if I can burn 100LL (hundred octane low lead aviation gasoline, which doesn't contain ethanol) in our Yamaha T-60 outboards? When we take the travel time into account, it's not THAT much more expensive, and it's readily available ten minutes from home. We don't use enough to keep the ethanol stuff fresh, even with stabilizer added.

I called a Yamaha guy over at Manteo who said he didn't have the definitive official answer, but he DID know that the state ferry ops nearby had an outboard on a runabout they hardly ever used, and had continuing problems with gummed-up carburetors. 

He hied himself over to the local airport, bought himself some gallons of 100LL, and has had no further problems. I think we may just go with that! 

At $5.50/gallon, it's not cheap, but neither is $4.05 for ethanol free, an hour's drive (or 6 hours of perfect weather by homemade houseboat) away. And carburetor teardowns are really pricey. The local outboard guy thinks he has a license to steal. Bless his heart.

*

SO: 

Does anybody know if she can burn 100LL (hundred octane low lead aviation gasoline, which doesn't contain ethanol) in her Yamaha T-60 outboards?


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## purple haze (Sep 2, 2013)

First I will say I DON"T KNOW but I would not put the 100 in and use it on a boat motor. My reason would be the 100 burns hotter then 87 or 93. Put that engine under a load which all outboards are on and you may have burnt pistons in no time. I had a friend many years ago when the feds took away lead and he refused to use it. We worked at a air field that 115/145 was available. Yep he used the 115 for about a week until he started burning pistons.


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## The Maintenance Shoppe (Nov 5, 2007)

The octane rating also known as "RON" is in reference to the resistance of detonation and preigniton. Higher octane DOES NOT BURN HOTTER. If it burned hotter and melted pistons, then every street racer across the country taking his daily driver to the track and pumping 116 octane Sunoco fuel in their car to blast down the track on the weekend would be replacing motors. Running 140 octane fuel for that matter will have absolutely no negative effects on on engine.

My concern is the low lead or LL content. If the motor is a four stroke, I would be concerned. I know when they changed from leaded to unleaded there were valve problems that were occuring.

100LL is pronounced "one hundred low lead". It contains about one-half the TEL allowed in 100/130 (green), though the amount is about 4 times what was in pre-1975 leaded automotive grade gasoline.[citation needed]

Many Continental and Lycoming light airplane engines designed for 80/87 remain in production. Engines designed for 80/87 and not for 100LL might have lead buildup and lead fouling of the spark plugs if 100LL is used.[citation needed]


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## NoMoSurf (Oct 2, 2007)

The Maintenance Shoppe said:


> The octane rating also known as "RON" is in reference to the resistance of detonation and preigniton. Higher octane DOES NOT BURN HOTTER. If it burned hotter and melted pistons, then every street racer across the country taking his daily driver to the track and pumping 116 octane Sunoco fuel in their car to blast down the track on the weekend would be replacing motors. Running 140 octane fuel for that matter will have absolutely no negative effects on on engines.


Correct. I used to run turbocharged japanese racing engines in our race cars. They were designed to be used with 98 octane. We used to run a mixture of 93 and 104 to make the 98 octane. I eventually killed one of them by running it on 93 while at low boost. It burned all 6 pistons because the octane was too LOW. The lower the octane, the less resistance it has to detonation. In a high compression situation (whether by compression ratio or by boost) the lower octane fuels will combust from the pressure of being crammed into the cylinder. The higher octane fuels have additives that inhibit this effect. Usually Toluene and a few others.


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