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Old 29-07-2016, 10:04   #31
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Re: aviation gas for a 20hp yamaha

Avgas used to have a higher octane rating.
If indeed automotive gas is composed of different hydrocarbon fractions, it might have more energy than avgas per gallon. Not likely to be significant in a 20 HP tender. Biggest effect of energy content is consumption.

My father used to keep scrupulous records of fuel usage in his boats, and cars.
I also used to. If you use Higher octane than an an engine requires, you will burn more fuel and produce less power. Not likely to tell the difference. You will have to average 10 or so tanks to get an accurate reading of the small difference. The accuracy of one full tank is much smaller than the difference

The effect of higher octane is very similar to retarding the timing.

Lower octane than required will be similar, low power, high consumption, and knocking. Much like advanced timing.

If changing to a different fuel than the engine was built for helps the situation , something could be wrong with the engine, and using said fuel might defer repairing the engine. BUT! If it really helps, the engine is bad. Best to fix the defective engine. Combustion chamber deposits come to mind. Avgas will speed up deposit formation.

Another possibility, is the power of suggestion.
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Old 29-07-2016, 10:19   #32
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Re: aviation gas for a 20hp yamaha

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those little bb,s means the motor is detonating and that is not good too much of that will definitely kill it. Detonation means the fuel is ignited prematurely and is extremely hard on things
No, it really is lead, his O-320 is one of the engines that don't "need" the extra Octane and really do run better and cleaner off of car gas, my little C-85 is another one that runs better off of car gas. The plugs in these motors will build lead deposits.
Back in the day when these engines were manufactured there were I believe three grades of aviation gasoline and the little motors ran on the low octane, cheap stuff, leaving the high powered super and turbocharged motor to burn the high Octane stuff, but since a pretty long time ago all that went away and there is only 100LL now.
Only reason I have 100LL in my little airplane now is it's storage life, I fly so infrequently that I do not want car gas in there, but the motor runs better and requires less maintenance with car gas than 100LL
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Old 29-07-2016, 10:45   #33
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Re: aviation gas for a 20hp yamaha

[QUOTE=a64pilot;2177708]High powered super and turbocharged motor to burn the high Octane stuff, but since a pretty long time ago all that went away and there is only 100LL now.

Out west in the US they still use old planes for fire fighting. These were the ones that use purple 145 oct avgas. Some models have added alc injection systems for take off. Some models have a small jet engine on each wing and they use avgas in it.
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Old 29-07-2016, 11:06   #34
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Re: aviation gas for a 20hp yamaha

The folks at Stabilant, who make that great pink gasoline additive that keeps gas fresh for two full years, also make a "Blue" Marine Stanilant that is designed to keep the moisture and alcohol properly emulsified, or in suspension, or whatever the correct mix is. Adding that to gasahol should ensure that it burns properly and does not do any damage to the engine, unless there are some engine parts which are so old they are simply attacked by the alcohol content. I think PS reviewed some similar products a couple of years ago, and that StarBrite had something similar as well. Both much simpler to obtain and cheaper than Avgas. And of course lead-free, fwiw.
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Old 29-07-2016, 11:22   #35
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Re: aviation gas for a 20hp yamaha

Gasahol, I haven't heard that term in about 40 years.
Bet there isn't a lick of difference
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Old 29-07-2016, 11:24   #36
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Re: aviation gas for a 20hp yamaha

Guy,
Some of the Garrett users of our airplane have rigged an alcohol water injection for takeoff to keep the EGT down, I have heard the blue windshield washer fluid is good for that.
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Old 29-07-2016, 11:38   #37
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Re: aviation gas for a 20hp yamaha

The Crown gas station in Easton, MD carries and sells no-ethanol auto gas. I know because I just purchased 10 gallon ($5 and change per gallon). Phase separation is the term that descibe the ethanol water compound that is so destructive to marine fuel systems and the corn lobby is pushing Congress to up the ethanol content to 15 percent. Pure politics and lunacy at its finest.
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Old 29-07-2016, 11:42   #38
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Re: aviation gas for a 20hp yamaha

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The Crown gas station in Easton, MD carries and sells no-ethanol auto gas. I know because I just purchased 10 gallon ($5 and change per gallon). Phase separation is the term that descibe the ethanol water compound that is so destructive to marine fuel systems and the corn lobby is pushing Congress to up the ethanol content to 15 percent. Pure politics and lunacy at its finest.

Wow, I'm running 10% ethanol, 87 octane which is what the manual says to use in my carbureted 2011 5 hp 4 stroke Mercury and it's about $1.74 a gallon at present

No problems over the past 5 years..............and I usually use up the fuel that sat in the external tank over the Winter first the following Spring
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Old 29-07-2016, 11:53   #39
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Re: aviation gas for a 20hp yamaha

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"Last, ethanol for a fact WILL cause the carburator to gum over and gradually make it start to stall out. And to me an unreliable engine is something that's useless."

This is not a fact, it's supposition. While there are scenarios where ethanol in gas can cause problems, it is possible to avoid them.

If you don't have a lot of water in your gasoline, or an old engine with incompatible materials in the fuel system, you will be fine.

The gum deposits you find in a used carburettor are present in all gasoline. Ethanol is a colorless alcohol which evaporates to leave no residue.

I've posted this advice a dozen times, so here's the thirteenth. The keys to a reliable outboard are :

Use fresh gasoline. When it's more than a month or two old, put it in your car and buy fresh.

Use Stabil in the fuel.

And most importantly, run the carb dry at the end of each use, or even better, drain the carb.

If you follow this advice, the engine will be reliable regardless of use of ethanol or not.

You are going to waste an awful lot of your time running around buying gasoline that's illegal to use in a marine environment.

I am the owner of outboards for 7 years now (Tohatsu 3.5 4 stroke, Yamaha 8hp 2 stroke), all run on ethanol gasoline, never cleaned a carburettor, always start up right away.
What he said.

The ethanol cuase gum is pure urban legend. I do a lot of fuel testing, and there is nothing in the performance or in the chemistry of ethanol that even suggestes that. Ethanol does not "react" with gasoline, and ethanol itself will not gum. Nonsense without support.

However--and this is a big however--there are a few things to watch.

1. Older systems could have have materials incompatibility issues. Not in the last 10 years.
2. Water absorption. This can lead to corrosion, which can be soavle 2 ways:
a. keep the water out. Close the integral tank EVERY TIME you stop using the motor.
b. install a silica gel vent filter. Last about 5 years before requireing easy regeneration.
3. Additives can fight corrosion. They make a lot of bogus claims, but corrosion protection is possible. I've done a lot of testing, am currently working with ASTM on a standard, but currently they can claim what they like. You safe bet from now is OEM brands; they are the only ones with a real interest. The aftermarkt guys are the ones fighting agains the standard, because they fear the light.

But no, there is no reason to use non-ethanol gas if it cost much more. Just get a good additive. I've been doing long-terms tests with Biobor EB, Merc Marine. Last week I broke down some 8-year old carbs for inspection and they were pristine. Never drained, never run MT, just treated gas.

It's chemistry.
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Old 29-07-2016, 11:56   #40
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Re: aviation gas for a 20hp yamaha

I will only buy top tier fuel myself, and I think to some extent that has helped

https://en.wikipedia.org/wiki/Top_Ti...rgent_Gasoline

Retailers
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Old 29-07-2016, 11:58   #41
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Re: aviation gas for a 20hp yamaha

"Gasahol, I haven't heard that term in about 40 years." Yup. E-5, E-10, E-15, E-90, they're all "gasahol". The fancier names or more specific ones have a purpose, but mainly to sell you something that has 10% less fuel density and lowers your mpg by at least that much, according to most reports to the EPA mileage site. Gasoline, it ain't. Bathtub gin is more like it.
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Old 29-07-2016, 12:03   #42
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Re: aviation gas for a 20hp yamaha

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Here is a list of the gass stations in MD that sell ethanol free fuel.

Ethanol-free gas stations in the U.S. and Canada

It's typically about 10% more expensive per gallon here than the mixed stuff, but we prefer it for the boat most of the time.
Problem Solved! I se WA state has 254 stations too! I buy from one listed often, it's at most $.10 higher per gallon than elsewhere usually.
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Old 29-07-2016, 12:30   #43
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Re: aviation gas for a 20hp yamaha

Schooner Dog. Lee Airport in Edgewater has ethanol free fuel for around $5.50 a gallon. I have a 10HP Honda that just loves it. It's the only place I know of near Annapolis that has it.
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Old 29-07-2016, 12:35   #44
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Re: aviation gas for a 20hp yamaha

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I think but am not sure, but sale of non ETH (ethanol) fuel is illegal, for any purpose.
That is why Avgas is illegal, way back in the 70's the law stated that the manufacture and sale of leaded gasoline was illegal, it didn't say except for Avgas, it meant gasoline for automobiles, but didn't say that.

Now here in Ga, it's not required to have ETH, but "may" contain up to 10% ETH.
The local Chevron Jobber is selling non ETH fuel to farms etc as he says that the ETH s acts like a solvent and you can't just put it in old tanks, they have to be cleaned, hoses replaced etc, and the average farmer that uses very little gasoline anyway just can't / won't do that, so he sells "pure" gasoline, I used to buy from him for my boat and airplane, carried a 100 gl tank in my truck for that purpose.

The fuel pumped in the pipeline is "pure" gasoline, the ETH is added by the Jobber at his facility, then trucked out, apparently the ETH causes problems in the pipeline.

It's my understanding that ETH's cost is much higher than gasoline is now, that to make economic sense gasoline has to be at $4 a gl, so by adding it, it;s driving the cost of gasoline up.

Maybe Urban myth, I don't know
Not sure about anhydrous, fuel grade ethanol but industrial 190 proof last I checked was around $1.20-$1.40/gallon wholesale. However I hear frequent comments from friends in the fuel business about how expensive it is to blend ethanol into gasoline but not sure why.

Regarding TEL in avgas, I used to work for a company that sold TE. It's been a few years but at the time there were still at least three that we sold to and we were not the only supplier. Chevron/Phillips and Koch refining were two that I recall we sold. I think Shell and BP also make avgas.

It was also still used for racing fuel. VP Racing and Sunoco were both blending leaded racing fuel.

I heard some small company was starting to blend a high octane leaded avgas but don't have any details.

TEL is really, really nasty stuff. So dangerous that we would give annual training sessions to the personnel at the customers' plants. Full hazmat suits and positive pressure respirators were required for anyone handling the material. I heard it was pretty unpleasant wearing a full suit in the SW in August while discharging isotanks.
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Old 29-07-2016, 12:57   #45
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Re: aviation gas for a 20hp yamaha

Why not just take out the alcohol? When I came in to Maryland after having used alcohol free fuel for years I filled up with a tank of ethanol drunken feel.

Within five minutes the engine quit. The drunken fuel had taken a little bit of water out of the bottom of the tanks but it accumulated over the years and cause the entire load of outhaul settle out on the bottom.

I siphoned off the water alcohol mixture from the bottom of the tank drain the water out of the carburetor started the engine and ran it for 40 gallons worth of fuel. By that point I have met made my way out of the drunken state back into an alcohol free state. You lie
I read a bit about fuel separation and the best Theory is when there's too much water for the alcohol dissolve the alcohol phase separates and the water drop to the bottom of the tank.

Someone smarter than me can make a phase separator and Sell ethanol to drivers of the boats so I can drive drunk and keep their engine sober
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