fuel quality

TinBoats.net

Help Support TinBoats.net:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

turbotodd

Well-known member
Joined
Dec 24, 2011
Messages
1,410
Reaction score
7
Location
72032
I think y'all might enjoy this. Hopefully you'll find it useful; just goes to show how today's fuel quality has changed-drastically.

Customer brings me a boat today; says it's been sitting, yaddya yaddya. The norm. Get it running he wants to go fishin'. Don't blame him, on a day like today. First thing I do is pull a fuel sample by disconnecting the fuel line from the carburetor and then use the boat's primer bulb to force fuel from the line and into a clear jar. Came out clean. I set the jar in the shop; was about 1/2 pint of fuel at the most. Pics show it, in a little glass jar. I lost the lid long ago. This is 100% fuel with zero ethanol content (I use test strips at work to verify), and no premix as this is a 4 stroke. He says he just bought the fuel and I don't doubt him. There's only ONE station locally that sells "straight gas" and from my own experience, it's got to be 93 octane to get it 100%. The 87 and 89 always had a little bit of ethanol in it, no more than 4% is what I've seen by testing over the last couple years.

First pic, I had just pumped the fuel into the jar. This was at 1:48pm when I took the pic.
gas1.JPG





Second pic, was exactly 2 hours and a minute later. 3:49pm, jar still sitting in the same spot, and nobody's touched it. That's moisture condensing in the jar, that's why the gas is cloudy. The jar was about 10 degrees cooler than when I first put the fuel in it! Evaporative cooling effect. I have a cool video to share too, if I can figure out how to get it from my phone to the PC.

gas2.JPG

Now what have we learned? How do we apply this knowledge? First thing's first. If you guys have noticed; over the last few years manufacturers have gone to low-permeation fuel tanks, that are more or less sealed up. That's why they swell; and the cheap ones swell and BREAK at the seam. Don't get a cheap tank. 6 gallons of fuel laying in the bottom of a hot boat is not my idea of fun; and if you're a smoker and out fishing while enjoying your nicotine, and your 6 gal tank busts, you're in for a big surprise. Anyway, a lot of folks have gotten the idea that it's better to use an older vented fuel tank. Well obviously our fuel is different than it was when tanks were vented like "the old days" (1990's and before), so in using a vented fuel tank, there stands a chance for evaporation. Based on what I'm seeing, it surely happens. Also, as it evaporates, it cools, and in humid climates, moisture will condense in the fuel-as seen by the jar test above. So, big deal right? Enter: Premix fuel.

Gas evaporates and; similar to water evaporting, not everything changes state. There's the chemicals left that are in the water, and with fuel there's the oil left, and other chemicals that don't evaporate. So now your fuel is junk. You started out at 50:1, and worst case scenario after a few weeks of sitting, 50% of the fuel evaporates. So you had 50:1 with 6 gallons, now you have 25:1 with 3 gallons; give or take. See a problem here?
 
Ideally keep your fuel in a dry spot out of the sun. Mine stays in the garage where temps don't vary as much as outside. That being said, I use an old metal tank from probably the seventies. I have left it in the boat outside during fishing season for weeks in direct sun and haven't noticed any appreciable evaporation. Now that I think of it, lawn tractor, cars, motorcycle, snowmobile etc all have vented tanks.
I see your point but I think it would take a long time sitting before it's an issue. Assuming non ethanol fuel of course.


Sent from my iPhone using Tapatalk
 
I work on aircraft fuel trucks. We sump them every morning before filling the first aircraft with them because of the condensation that builds inside the tanks due to weather changes. We sump every incoming load of fuel we receive and the tank after the receipt to make sure we get rid of as much water as we can. We filter fuel for water and contaminates during every transfer of fuel whether it be truck to tank, tank to truck or truck to plane. We have a special tester that measures parts per million of water to fuel to test fuel. You are not going to get rid of all the water but you can try to keep it as "dry" as possible.
 
What I wonder is what kind of "damage" is done to the fuel after evaporation takes place? Again, correlating with, say, seawater, when it evaporates, the salt and other minerals are left over. With fuel, what's left after evaporation? And is it any good to run in an engine? Only curious, since I'm ignorant of the chemical composition of modern gasoline.
 
I do have 3 gallon plastic attwood tank from Cabela's. It does swell a good deal in the sun. Since most of my local waters are no wake I don't use much fuel to begin with, so I basically only have a gallon or so in the tank at any given time. I don't trust any gas sitting for more than a month.
 

Latest posts

Top