Adding straight gas to mix

[bluebackfisher]

I have often wondered if it’s OK to add some straight gas to the fuel/oil mix in my boat‘s gas tank after being stored for a few months over winter. I have noticed that the boat is much harder to start and smokes much more in the spring when I am summarizing the boat? I am aware that gasoline will evaporate out of the mix with my older 1992 vented gas tank on my Bayliner.

 

[Scott Danforth]

no. do not do that.
what has evaporated is the fuel in the carb, so your carb has a bit extra oil. just run it, let it smoke a bit and then the extra smoke goes away after a few minutes.

 

[racerone]

Agreed-----Do not do that.----I am not even sure that the oil that was mixed last year is still the same quality.------But good you asked the question.-----But question like these also indicate to me that the whole concept of 2 strokes and the mixing of gas and oil are not well understood.

 

[jerryjerry05]

Add more if you have room but add pre-mixed gas/oil.
If the gas has only sat for a few months it shouldn't go bad.
What can happen is if the tank is not full and the boat sets in the sun, condensation forms and water settles in the bottom of the tank.
Raise the bow as far as you can, add 3-4 dry gas or 1/2 qt. of camping stove alcohol, this will help absorb the water.
Any boat with a built in tank should have a water separating filter in the system. Change that filter once a year or check and drain it often.

 

[bluebackfisher]

no. do not do that.
what has evaporated is the fuel in the carb, so your carb has a bit extra oil. just run it, let it smoke a bit and then the extra smoke goes away after a few minutes.

Thanks, that makes sense!

 

[bluebackfisher]

Add more if you have room but add pre-mixed gas/oil.
If the gas has only sat for a few months it shouldn't go bad.
What can happen is if the tank is not full and the boat sets in the sun, condensation forms and water settles in the bottom of the tank.
Raise the bow as far as you can, add 3-4 dry gas or 1/2 qt. of camping stove alcohol, this will help absorb the water.
Any boat with a built in tank should have a water separating filter in the system. Change that filter once a year or check and drain it often.

Thanks for the reply, I only run non- ethanol fuel in the boat and add startron fuel stabilizer to the fuel. In the summer it does sit out in the sun a lot, but I heard that adding gas dryer to fuel/oil mix can hurt a 2 cycle outboard? I will definitely install a fuel/water filter on her.

 

[bluebackfisher]

Agreed-----Do not do that.----I am not even sure that the oil that was mixed last year is still the same quality.------But good you asked the question.-----But question like these also indicate to me that the whole concept of 2 strokes and the mixing of gas and oil are not well understood.

Thanks for the reply, I think if I drain the fuel out of the tank at the end of the season this may help matters?

 

[dingbat]

I only run non- ethanol fuel in the boat and add startron fuel stabilizer to the fuel.

That could be part of the problem.
What fuel system cleaner do you use, if at all?
When was the last time you drained and cleaned the fuel system, tank included, and decarbed the motor?

but I heard that adding gas dryer to fuel/oil mix can hurt a 2 cycle outboard?

Nonsense….. I burn at least 40 gallons of “gas dryer” through my outboard every year. Keeps the fuel system nice and clean while preventing a buildup of moisture in the fuel tank

 

[nola mike]

Ethanol fuel does a good job of absorbing excess water in the tank (up until a point).

 

[jerryjerry05]

Ethanol fuel does a good job of absorbing excess water in the tank (up until a point).

Where'd you hear that?
Worried about condensation? Using Ethanol or not if the tanks full when not in use, then condensation can't form.
Ethanol seems to draw/attract moisture no absorb it.
If the boats gonna set, even with a full tank and your using Ethanol fuel then use E stabilizer, the fuel in the lines can eat the hoses and moisture can form in the carb.
Depending on the motor, you can drain the carbs fairly easy.

 

[nola mike]

Where'd you hear that?
Worried about condensation? Using Ethanol or not if the tanks full when not in use, then condensation can't form.
Ethanol seems to draw/attract moisture no absorb it.
.

Didn't hear it so much as that it's science. Ethanol (and other alcohols) absorb water until they phase separate. Straight gas has no ability to hold water. That's why you add "dry gas" products--which are essentially straight methanol. Condensation can happen regardless of what's in your tank, if the tank isn't sealed.

https://cropwatch.unl.edu/documents/Ethanol%20and%20Water%20Contamination%2009052014.pdf

 

[dingbat]

Ethanol seems to draw/attract moisture no absorb it.

Are you sure about that?

“Ethanol does not "grab water molecules out of the air." It is hydrophilic, which means ethanol holds water. With regular gasoline (E0) as well at E10, the primary cause of water collecting in tanks is condensation on tank walls. But unlike E0, which can absorb almost no moisture, E10 can hold up to half of one percent of water by volume, and the water molecules will dissolve in the fuel. The "solubilized" water will bypass the water separator and burn harmlessly through the engine.”