Av gas

[smallblock]

Am I better off running aviation fuel through my outboards? Im fed up with replacing floats. I have heard it has a higher lead content which could cause more build up but wouldnt that be better than using the garbage at the pumps? Thanks for any comments about using this...

 

[JB]

Re: Av gas

You are better off using the fuel your outboards were designed to use. . . 87 octane unleaded.

 

[smallblock]

Re: Av gas

Thanks JB. This outboard was built while the gas had a higher lead content and didnt contain Ethynol and most likely of higher octane. So I guess Im confused by your answer, the Av gas is closer to the old gas then the gas available at the pump currently? I should get longer than a month out of a new float before the varnish comes off and ends up floating around the fuel bowl...

 

[gss036]

Re: Av gas

I would suspect that if you are not buying OEM floats, then the ones you are buying are of poor quality. More information would be helpful. I agree with JB, stick to 87 octane regular gas. AV gas is much higher and probably would damage your engine over the long haul.

 

[antique fisherman]

Re: Av gas

Av Gas is 100 octane low lead. It burns hotter = engine damage. Some race car drivers use it in race cars, but, in our cars it will burn pistons and valves.
P L E A S E don't burn up a good boat engine.

 

[JB]

Re: Av gas

Sorry. I missed where you told us the model numbers of your outboards.

It doesn't matter, though. 87 unleaded is as close as you can get to the old 80 octane white gas we used for many years.

 

[Brewman61]

Re: Av gas

Lead in gasoline was put there for octane and such. I'm not sure it impacts fuel floats at all. The lack of lead in your gas certainly isn't the problem with your carb. It's possible that ethanol could be an issue.
In this area we can find certain gas stations that sell gasoline that is ethano free. Only premium grade gas though. But it won't hurt an engine designed to burn 87 octane to burn 92. That's what our marina sells, anyway- ethanol free premium. I pay extra for not having to deal with ethanol though my boat and engine are certified for the 10% max stuff.
Try doing a google search on ethanol free gasoline and see if it's avaialble in your area. Costs about $0.50/gallon more than regular.

 

[KeyWestSkipper]

Re: Av gas

Am I better off running aviation fuel through my outboards? Im fed up with replacing floats. I have heard it has a higher lead content which could cause more build up but wouldnt that be better than using the garbage at the pumps? Thanks for any comments about using this...

I haven't used it so I can't vouch, but I've seen a made-for-boat fuel called ValvTech at some marinas, which claims to be significantly better for boat motors than the regular stuff. Maybe that's another option.

 

[rodbolt]

Re: Av gas

av gas,as any high octane fuel, burns cooler than 87 in the same compression range because it burns slower than 87.its why in grannys grocery getter the engine had about 8 to 8.5/1compression and our 427 we raced had custom manly pistons at 13.5/1.
grannys grocery getter ran fine on regular,the 427 wanted a bit higher octane to prevent detonation.
difference was how tight the air/fuel mix got squeezed.
same 14.7/1 air fuel mix just squeezed different.
kinda like nitrous injection,if done correctly combustion pressure increases but combustion temp decreases.
av gas we used to get was blue gas at 110 octane but the reed vapor pressure wasnt correct and sometimes hot restarts were a bit tricky and we had to run a fuel cooler.
airplanes typically run a few feet higher than cars.
two strokes ALWAYS hated leaded fuels, to much deposits.
lead was added not only to slow the burn rate but mostly to cushion the valves.
two strokes dont have them.
some cork float shellacs cant tolerate E fuels.

 

[PGFISHER]

Re: Av gas

I agree, gasoline is gasoline, the additives make the difference. Ethanol may very well be the cause of your problems, higher octane isn't the answer. Higher octanes don't increase horsepower; they only burn slower. As octane increases, the gas burning slower will keep heat in the cylinder longer, overheating the engine. Run the lowest octane that doesnt ping; anything higher is a waste of money.

 

[cougar1985]

Re: Av gas

I agree, gasoline is gasoline, the additives make the difference. Ethanol may very well be the cause of your problems, higher octane isn't the answer. Higher octanes don't increase horsepower; they only burn slower. As octane increases, the gas burning slower will keep heat in the cylinder longer, overheating the engine. Run the lowest octane that doesnt ping; anything higher is a waste of money.

ahhh youve hit on one of my pet peeves!the fallicy of high octane equals better running and better and fuel milage .all engines are designed to run at optimum at a certian grade or octane rating,anything else your just fooling yourself and wasting money.

 

[Frank Acampora]

Re: Av gas

Well, Smallblock, your wording of your post makes it appear that you do have an attitude that Big Brother is out to get you- Quote---Garbage at the pumps----

However, if you are having a continuing problem with floats, why not try painting them with a high quality epoxy paint before use? Petit Model airplane Hobbypoxy brand comes to mind. It is alcohol, nitro, oil, and gasoline resistant. Been many years, hope they still make it.

 

[smallblock]

Re: Av gas

Wow! Thanks for the honest replys and valuable information(especially grannies grocery getta lesson on compression ratios). I wasnt try to achieve a higher octane, only a fuel without alcohol in it. I did however find a product made of methyl ethyl ketone and acetone that claims to be gas,alcohol and oil proof. Its called Seal-All and its made by Eclectic Products. I am going to coat my floats in it and see how it goes...
My attitude against "big brother" is apparent I guess. I mentioned Av-gas because I run it in a Chevelle that doesnt like pump gas, and use it as storage fuel for small engines. Again thanks for the information.

 

[rodbolt]

Re: Av gas

years ago I purchased a granny grocery getter, litteraly.
old woman was going into a nursing home and sold me a 1965 olds dynamic 88 with a ultra high compression rocket 425.
compression ratio was 10.5/1.
this was in 1980.
running on super shell 98 octane it idle at 450 in gear and so smooth you could balance ciggertte on the air filter.
stomp the gas and it would burn rubber mostly throuh second gear.
fill it with 87 regular and it bucked snorted farted and pinged and would not get out of its own tracks hardley.
however the owners manual stated 95 octane minimum.
my 1970 W-30 442 was even worse cause I added 11.5/1 pistons and the luanati w-30 cheater cam and a few other goodies.
my wifes bone stock 71 cutlass converable with a 350 2bbl and 8/1 pistons would run about anything and still get 20 MPG on the highway.

 

[pine island fred]

Re: Av gas

Where are you guys getting all this 100 LL? FBOs are supposed to pump it only in aircraft and cant even use it in their own ground equipment. If you can get it, good for you but dont broadcast it. Cant think of any problems burning it. Works real good in air cooled aircraft engines. RODBOLT, sorry I could not make it. Had to go back go back to ROANOKE from N.J. From there to OBX is 400 miles. Did consider the trip but from OBX to home is 950 mi. Hopefully some other time. FRED

 

[Bigperch]

Re: Av gas

Fred,

You fly home and siphon it into a can.

 

[rodbolt]

Re: Av gas

any airport will sell you the av gas.
we had to sign an affidavit stating it was off road use only cause its not taxed with state or federal road tax.
kinda like here, if you buy marina gas and they charge road tax you can apply for a refund of the tax at the end of the year if you keep the reciepts.

 

[robert graham]

Re: Av gas

My son runs 93 octane automotive pump gas in his Cessna 172 whenever he can just to avoid the $5/gallon FBO aviation gas prices. It runs just the same, but the plane does have the advantage of a mixture control on the instrument panel and an exhaust gas temperature guage, so adjustments can be made in flight for altitude and efficiencies. The 87 octane pump gas is fine for most outboards. Why heck, the compression ratio on my 90HP 2 stroke is only about 6:1 Clean, fresh fuel is lot more important to an outboard than octane ratings. My $.02...

 

[antique fisherman]

Re: Av gas

My son runs 93 octane automotive pump gas in his Cessna 172 whenever he can just to avoid the $5/gallon FBO aviation gas prices. It runs just the same, but the plane does have the advantage of a mixture control on the instrument panel and an exhaust gas temperature guage, so adjustments can be made in flight for altitude and efficiencies. The 87 octane pump gas is fine for most outboards. Why heck, the compression ratio on my 90HP 2 stroke is only about 6:1 Clean, fresh fuel is lot more important to an outboard than octane ratings. My $.02...

I hope that your son has a STC (supplemitial type certificate) for his plane. It's illegal to use auto fuel in it without a STC.

 

[robert graham]

Re: Av gas

I'm not familiar with that and not sure if he is either, but when you're parked next to some strip without a fuel pad, you just take your 5 gallon container down to the local 7/11 and get some gas. My boy says it runs just fine, but I'm confident there's some law says you can't do it! He flys in and out of some pretty out of the way places and they camp under the wings. What's the old man gonna do, tell him he can't do it?