Race gas ????

[chris3298]

I understand the reason for high octane race gas is when you have so much compression well you need that higher octane to start the motor and to run right. VP racing fuel has so many different names for there fuel if I wanted to build a motor that clearly needed to run on higher octane race gas what would yall recommend or simply go by the octane rating? I have heard of people running there outboards on aviation fuel now from what I have read is the avgas is about 100 octane at sea level but as a plane climbs in altitude the octane goes up to about 130. I have also heard that avgas is very dry but is it safe to run in an outboard motor? I have looked up online of websites that tell you how much the avgas is in your area and well it's a lot cheaper then racing gas and the other question is well can you get it not being a pilot. I maybe able to get it near me I'm thinking.

So can someone please tell me is avgas safe for an outboard motor and what brands of high octane race gas do you like for your outboard?

I tried the search but didn't find anything on this subject.

Thanks
Chris

[Bill Van Steenwyk]

I understand the reason for high octane race gas is when you have so much compression well you need that higher octane to start the motor and to run right. VP racing fuel has so many different names for there fuel if I wanted to build a motor that clearly needed to run on higher octane race gas what would yall recommend or simply go by the octane rating? I have heard of people running there outboards on aviation fuel now from what I have read is the avgas is about 100 octane at sea level but as a plane climbs in altitude the octane goes up to about 130. I have also heard that avgas is very dry but is it safe to run in an outboard motor? I have looked up online of websites that tell you how much the avgas is in your area and well it's a lot cheaper then racing gas and the other question is well can you get it not being a pilot. I maybe able to get it near me I'm thinking.

So can someone please tell me is avgas safe for an outboard motor and what brands of high octane race gas do you like for your outboard?

I tried the search but didn't find anything on this subject.

Thanks
Chris

All the info I can give you is from my own personal experience, and this experience is some 30 years old now, as it took place in the late '70's and early to mid '80's, except for one instance a couple of years ago. I used it in a Yamato 80 that my wife raced 10-12 times a year for 5 years plus the normal testing done at a race. The type was leaded 100 octane.

That being said, I do not believe that av gas has changed that much in the intervening years, except for the fact that some grades now are either NOT leaded, or have a very small amount compared to years ago. They achieve the no-knock ability with other additives instead of lead. Also you will find no ethanol in Av gas, which is a plus. Ethanol will attract moisture right out of the atmosphere and that is a bad deal for gas used in airplanes, as temp goes down as altitude increases, and the danger of the water in fuel freezing and blocking fuel lines is a real no-no when you are not on dry land.

The comment about Av gas being "dry" came originally, if not mistaken, for the fact it (some grades) contained no lead and burned "dry" meaning that since it had no lead, it was hard on valves, as one of the reasons for lead was to lubricate the valve seats. I burned it one time for several months in a '50's model car and burned the valves.

Since a two stroke has no valves, and if you use a good oil (I used a degummed castor oil called Blendzoll) I would not be afraid to use it. Many of the OPC guys that run SST140, Champ Boat, and other classes with two strokes have used it for years, probably with regular OMC or Merc oil.

As far as availability, I would think you would want to stay away from large airports with commercial flights and use the smaller strips that service mostly private aircraft. A perfect source could be a crop duster strip. I know of no law prohibiting (I could be wrong) the sale of Av gas to individuals, but I do see some comments on here from time to time where some have had difficulty purchasing at larger airports because of rules prohibiting dispensing of Av gas except into aircraft. That probably would not be an issue at a smaller facility. I filled my bass boat at a small local airport several years ago until I found a suitable source for non-ethanol laced fuel because of problems with it in marine use. Expensive but available.

Hope that helps.

[chris3298]

All the info I can give you is from my own personal experience, and this experience is some 30 years old now, as it took place in the late '70's and early to mid '80's, except for one instance a couple of years ago. I used it in a Yamato 80 that my wife raced 10-12 times a year for 5 years plus the normal testing done at a race. The type was leaded 100 octane.

That being said, I do not believe that av gas has changed that much in the intervening years, except for the fact that some grades now are either NOT leaded, or have a very small amount compared to years ago. They achieve the no-knock ability with other additives instead of lead. Also you will find no ethanol in Av gas, which is a plus. Ethanol will attract moisture right out of the atmosphere and that is a bad deal for gas used in airplanes, as temp goes down as altitude increases, and the danger of the water in fuel freezing and blocking fuel lines is a real no-no when you are not on dry land.

The comment about Av gas being "dry" came originally, if not mistaken, for the fact it (some grades) contained no lead and burned "dry" meaning that since it had no lead, it was hard on valves, as one of the reasons for lead was to lubricate the valve seats. I burned it one time for several months in a '50's model car and burned the valves.

Since a two stroke has no valves, and if you use a good oil (I used a degummed castor oil called Blendzoll) I would not be afraid to use it. Many of the OPC guys that run SST140, Champ Boat, and other classes with two strokes have used it for years, probably with regular OMC or Merc oil.

As far as availability, I would think you would want to stay away from large airports with commercial flights and use the smaller strips that service mostly private aircraft. A perfect source could be a crop duster strip. I know of no law prohibiting (I could be wrong) the sale of Av gas to individuals, but I do see some comments on here from time to time where some have had difficulty purchasing at larger airports because of rules prohibiting dispensing of Av gas except into aircraft. That probably would not be an issue at a smaller facility. I filled my bass boat at a small local airport several years ago until I found a suitable source for non-ethanol laced fuel because of problems with it in marine use. Expensive but available.

Hope that helps.

Thank you Bill,

I just spent about the last hour trying to dig up what ever I can find about avgas and seems a lot was just the normal bad old rumors about it but most what I read was good. Down here in Louisiana it's still easy to find the non ethanol gas but I'm want to hop up this motor I have and well wanted to make sure the avgas is safe for outboard because it is clearly cheaper then the race gases. There is a small airport about 10 minutes from me that sells the 100LL says it is a self service fueling station and I have not gone and talked to them yet but I have no doubt I should be able to buy it from them and if not well there are several other smaller airports around. Other than the brand oil you use to mix in the gas I assume there isn't any kinda special oil to mix with the 100LL fuel to be run in outboards is there?

I had also read not sure if true but that avgas stores well for long periods of time is this also true? or should I be using any kinda marine sta-bil with it to?

Thanks for sharing the info,
Chris

[Bill Van Steenwyk]

Thank you Bill,

I just spent about the last hour trying to dig up what ever I can find about avgas and seems a lot was just the normal bad old rumors about it but most what I read was good. Down here in Louisiana it's still easy to find the non ethanol gas but I'm want to hop up this motor I have and well wanted to make sure the avgas is safe for outboard because it is clearly cheaper then the race gases. There is a small airport about 10 minutes from me that sells the 100LL says it is a self service fueling station and I have not gone and talked to them yet but I have no doubt I should be able to buy it from them and if not well there are several other smaller airports around. Other than the brand oil you use to mix in the gas I assume there isn't any kinda special oil to mix with the 100LL fuel to be run in outboards is there?

I had also read not sure if true but that avgas stores well for long periods of time is this also true? or should I be using any kinda marine sta-bil with it to?

Thanks for sharing the info,
Chris

I would say the thing to be concerned about is just to be sure you have not modified the engine are planning on using with too high compression ratio so as to incur detonation. If you have not modified the head to bring the CC's down, there should be no problem. Don't believe you mentioned the type/make motor, but lots of the more modern engines have knock sensors now, and retard timing or some other way to stop the problem if it starts.

I have no knowledge if the av gas lasts longer in storage than other types, but that would make sense, as unless operated by a flying service for hire, most airplanes owned by individuals are flown infrequently, and the gas in the tanks would have to be able to withstand long storage periods. Most, if not all airplanes I have been around, have "sump" drains to allow water (if any) to be drained from the fuel tank before flight, and that is part of the preflight process. Water will separate out from the fuel and stay on the bottom of the tank, and is very easily drained until gas starts to appear so as to eliminate the problem. Of course the FAA still finds accidents caused by water in the fuel, but that is mostly stupidity and not checking for it as a cause of an accident. The engine usually quits for this reason just about the time you break ground and there is no chance to go back to the airport.

As to additives for av gas, check the Sta-bil or Staron sites, and there is probably info there on the feasibility of using the product for av gas. As mentioned, the hardest part is finding someone to sell it to you, and looks like you have that whipped.

[Powerabout]

All Av gas has lead its rated in MON ratings
100 LL still has way more lead than pump gas ever had, its blue.
the one called 100 is the old 110-130 that has lots more lead, its green
Yes it last longer in storage as that is the spec
The spec also says its the same worldwide so if you run a race program using it its one less thing to tune to as when you buy it its the same everywhere
Another bonus these days for those of you in the US is it doesnt contain any alcohol

Race fuel is more expensive as it does other things and thats a whole other thread
Just remember that avgas was made for engines that did less then 4000rpm 60 years ago and F1 cars run EU spec pump gas

[David_L6]

Chris,

I've run quite a bit of AV gas with no problems whatsoever - either buying it or running it. I have run it in everything that I own that doesn't have smog controls - several different boat motors, weed eater, chain saw, both 2 stroke and 4 stroke dirt bikes, 4 stroke ATVs, 4 stroke lawn mowers...
Where I buy AV gas is closer to home than where I used to buy VP C12 and AV gas costs less. I buy it in Shreveport at either a "bulk" station (Smith Oil Co. on North Market) or the Downtown airport. Nothing special about mixing it. I use the same oils and mix it the same way as I would with automotive gas or VP C12.

[David_L6]

Chris,

Check this site: http://www.100ll.com/showfbo.php?Has...8126aa2499b2ee

[chris3298]

Same here David to find the racing gas I would have to drive probably another 45 miles while the little airport is so much closer. Seems like i keep reading about this people putting it in there chainsaws and riding mowers which probably is a great thing to do for end of the season when it's just sitting there all winter long and not running.

Bill this motor I've got is a 1986 56 ci Johnson and wanted to have it finger ported and and the head milled for more compression and what ever else could be done for more power. I just about got all the parts I need to build this motor which the powerhead being the hardest to find at this point. I'm still reading and learning of what all can be done. This won't be a ride around cruising motor it will be built for speed thats it.

Thanks
Chris

[Bill Van Steenwyk]

Chris:

I have no idea whether your motor has a knock sensor or not. If so, it would probably be a small plug type assembly screwed into the head with a wire coming out of it. That is the way mine are made and located on my Merc EFI 150. If your motor is not computer controlled and fuel injected, then I doubt it has the knock sensor available, either on the motor now or available as an add on without much cost and effort.

If you do the mods you are speaking about, I see no reason why 110LL Av gas would not be suitable for you to run for the reasons you list in your post, i.e. preventing detonation. If 100LL did not work for you, you could always go higher in octane, or there are octane boosters available you can add to the gas.

If I were in your shoes, I would make the mods, or have someone knowledgeable do it for me if I did not have the equipment required, fill the tank with 110LL and have at it. You can tell pretty easily by examination of the spark plugs/piston tops if detonation is occurring and then go from there. The main thing is don't run it hard but for a short time first time out before checking the indicators for detonation. There is a group here on BRF that frequent the "SMACK" forum, mostly from the south, La., Miss., etc. that have much experience with the 3cyl OMC and Mercs. They could probably be some help with just how far you can go before low octane gas becomes a problem. Spark knock and detonation are mostly an issue of CC's/compression ratio and spark lead or total advance on the ignition. Additional porting, not so much.

Have fun!!



ADD:

Also check out the thread entitled "The Mod 50's", or similar title, by "Fast Fred", listed under the tech forum as a "sticky" about number two or three down the list. Very informative information to improve performance on the 3 cyl OMC motors.

[chris3298]

Bill I have read a lot of the mod 50 sticky and yes it is a dam good read. This motor is a carb motor and sure it has no knock sensor to it. I have been to the races in Bogalusa and raced once there, man I'm hooked it's so much fun, this is why I am building this motor. Thanks for all the info about the avgas I still have a lot to learn. I plan on someone else doing all the machine work ad probably will let them assemble it as well now if it craps out down the road then I'll break the manual out and start learning how to assemble it and all myself which to really afford to do this I will have to learn myself eventually.

Thanks for all the help
Chris