2-Stroke Oil/Gas Mixture

Bassn7

Seaman
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May 25, 2015
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65
Is there any way to test my gas for the proper mixture? I want to be sure my new motor is being run properly. I don't want to over or under oil the gas mixture. AND.. what have you found to be the best method when filling the tank that's not completely empty? This seems to be a tricky step. Thanks for any help.
 

ondarvr

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Apr 6, 2005
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11,527
If you wanted to send the fuel off to a lab they could probably tell you if it was at 50:1, other than that...no.

Filling the tank can depend on the type and size of tank, but don't over think it, 2 stroke oil mixes easily with the gas, so it doesn't take much effort to get it right.

And it doesn't need to be exactly at 50:1 for the motor to survive into old age, close is good enough.
 
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Scott Danforth

Grumpy Vintage Moderator still playing with boats
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if you have pre-mix already in the tank, estimate what you are going to add and put in the appropriate amount of oil. not that hard. if I recall, 2.56 ounces of oil per every gallon of fuel
 

Grub54891

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I simply add the fuel, see how much it took and add the correct amount of oil, even the short drive to the lake mixes it well enough.
 

Silvertip

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Sep 22, 2003
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How about telling us exactly what this motor is! You said NEW motor! Since new motors (two strokes) are oil injected, why are you worried (and moreover, why are you adding oil to the gas)? If it's a four stroke, don't even think about adding oil to the gas. You add it to the crankcase just like your car. If you do NOT have a NEW motor and it is indeed a two stroke and it is not oil injected and you are needing to premix, the process of determining the amount of oil to add is really simple. 50:1 is one pint of oil in six gallons of fuel. Or 1/2 pint of oil in three gallons. You pump six gallons of gas and add a pint of oil. Pump another six and add a pint of oil. Continue until full. If you can't get six gallons in after adding the last oil, note how much you did get in. If it was 3 gallons or very close, add 1/2 pint. If was a gallon and half, add 1/4 pint. If the tank was quite full, you might want to use the 3-gallon/1/2 pint process since you may not get six gallons in the tank before it is full. Simple. By the time you leave the pump the oil and fuel will be mixed.
 

Bassn7

Seaman
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May 25, 2015
Messages
65
My motor was new to me...not brand new. A 1980 50 HP Mercury 4 cylinder 2-stroke. I just don't want to gunk it up with excess oil. Thanks to all who responded.
 

GA_Boater

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May 24, 2011
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I think Bass is asking about his early 80's Merc 50 2 stroke.

I add gas to the tank and stop when it's almost full on the closest 1/2 gallon. Using one of the handy dandy measuring bottles, add the oil to the line and pour it in the tank. By the time I get to the lake it's all mixed.

oilbottle.PNG
 

ondarvr

Supreme Mariner
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Apr 6, 2005
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I have several of those bottles around, they make it very easy to get the mix right, fill to the correct line and dump it in.
 

GA_Boater

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The bottles don't need charging or an App download.

And only cost about 5 bucks or less if it goes overboard. :smile:
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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the side of the bottle has a label that comes with it for free that says for 50:1, mix 2.56 ounces per gallon
 

Chris1956

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Mar 25, 2004
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27,033
Gee, a 50HP motor will likely have two 6 Gal portable tanks, or a permanent tank of 18 Gal or less. It is very easy to get those correctly filled with 50::1 fuel mix.

​For portable tanks, run 1 dry, and then switch over. When you are due to gas up, put 1 pint oil in the dry tank and fill it. Now look at the partially full tank. If less than 1/2 full, dump 1/2 pint of oil into it and add 3 gallons of gas. You should easily be able to tell if she is 1/2 full or less. If not, the gas will have an once or two extra oil. Not a big deal.

​For permanent tanks, add 6 gal gasoline and then dump in a pint of oil. Repeat until she gets nearly full. Now add 1/2 pint oil and 3 gal gas, until she is full. Again, if you misjudge the gas by a gallon or two in an 18 G tank, it is not a big deal......


Happy fueling...
 
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