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WakeWorld Discussion Board » >> Boats, Accessories & Tow Vehicles Archive » Archive through March 18, 2009 » Heres a question, 100LL Avgas in a Mercruiser? « Previous Next »
By Kelly (weskel) on Monday, June 16, 2008 - 1:12 pm:    Edit Post Delete Post
I have been around aircraft my entire life and back before catalytic converters we used to run Avgas in all our vehicles, mine in particular was a 1979 Chevy pickup with a 350 / 5.7L in it.

Long story short, my fathers friend owned an airport and had a very large fuel tank that partially was washed out of the ground by heavy flooding rain. The insurance paid for the tank and the thousands of gallons of fuel. You could no longer use the fuel for aircraft due to contamination, but it was perfectly fine for our trucks; so I did not pay for gas for about a year and a half.

That being said, I ran Avgas in my chevy for over 18 months with zero ill effects. My boat has a 5.0L Mercruiser in it (chevy 305) non fuel injected standard carb.

My question is has anyone ran straight 100LL in there boats or a mixture of auto gas and 100LL?

The reason I am asking is I have access to alot of waste Avgas due to the work I do at local avagas. Now keep in mind there is nothing wrong with "waste" gas, it just cannot be put back into aircraft with out a special filtration system.

With todays gas prices if I could use a blend of avgas/auto gas it would save alot of beer money...

Opinions and 2 cents please.....


By rodney (azwakekid) on Monday, June 16, 2008 - 1:35 pm:    Edit Post Delete Post
it will actually make your boat run better. and the gas wont go bad if you have it in your carb over the winter. and it will lube your upper end. i run avgas in my quad and lawn equipment and i dont see any problems with them. and i know that most of the guys that race flat bottoms. mostly k and ss run it in there boats. my .02
By Paul (psudy) on Monday, June 16, 2008 - 1:40 pm:    Edit Post Delete Post
I was under the impression that it was illegal to run 100LL on the street. Every time I purchased it for my race bike they had to ask me what I intended to use it for. As long as I responded for off road use it was ok. I could be dead wrong on this though.
By AtTheLake (bmartin) on Monday, June 16, 2008 - 2:02 pm:    Edit Post Delete Post
What is 100LL / AVgas? Where do you get it? Costs?
By Art (rallyart) on Monday, June 16, 2008 - 2:28 pm:    Edit Post Delete Post
Av gas has a much higher lead content that leaded auto fuel had. So that's going into the water and air behind the boat. It also has a higher octane rating than the boat needs which means it burns slower and you get a fraction worse mileage, and a fraction less power.
It has lower vapor pressure than auto or marine gas so you are less likely to get vapor locking on hot days but it would take longer to start on cold mornings.
Like rodney said it's more stable and last longer.

Biggest problem is all the lead going into the lake.

By Scott Legge (w00taz) on Monday, June 16, 2008 - 2:37 pm:    Edit Post Delete Post
I personally wouldn't run it in my boat (fuel injected) because it's under warranty. Who knows what it could do to the fuel injection system.

100 = Aviation calculated octane level and LL means low lead content. Meaning there is still some lead in this fuel.

By shredhead (shredhead) on Monday, June 16, 2008 - 2:42 pm:    Edit Post Delete Post
$5.60/gal this last weekend in the MW.
It's only illegal because of the lack of road tax, same with boat diesel.

By Kelly (weskel) on Monday, June 16, 2008 - 3:26 pm:    Edit Post Delete Post
It is alot more expensive if you have to buy it, I am an aircraft mechanic in my free time from the USAF and I am always working on cessna's, piper's, etc. In my hanger I have a couple 55 gallon drums for "waste" fuel.

I may get blasted for this, but I'm not to worried about the lead coming out of the boat, I run in salt water so there is more water to delute it down....

I was under the impression withthe higher octane you get better milage and better power???

By Kelly (weskel) on Monday, June 16, 2008 - 3:28 pm:    Edit Post Delete Post
Also forgot to add, Avgas exhaust smells better!!!!
By Scott (chilidog) on Monday, June 16, 2008 - 4:12 pm:    Edit Post Delete Post
When we would run out of gas in our trucks on a dirtbike trip we would throw in 2 stroke and it never hurt anything, seems this stuff may be better, the 2 stroke has oil in it and it never hurt my injected truck, so I'd say run it, I wish you were on the west coast I'd help relieve you of some of that pesky waste fuel......
By will5150 (will5150) on Monday, June 16, 2008 - 6:08 pm:    Edit Post Delete Post
the only thing i have heard is switching BACk to regular unleaded can really foul up your lines 'cause leaded and Av gas leave deposits in the fuel system that coat the lining and can foul plugs, and clog lines
By TXSurfVLX (bac) on Monday, June 16, 2008 - 6:31 pm:    Edit Post Delete Post
Kelly, a higher octane fuel will only do so much for a setup not meant for a high octane rating. Like putting in 93 instead of 87 in a car that only needs 87, you won't have much noticeable difference, if any. Art nailed it in his reply. Now, if your boat engine was high performance and you had a computer that you could tinker with for fuel settings or it was build to run on 100 gas, then if you put in something lesser, you would be knocking like crazy. There is no real advantage to purchase av gas over pump gas for mileage or power in the average boat, however if I had 55 gallon drums of it sitting around, I would use it too

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