Oil mix ratio, TCW3?

[otis24]

Pulled a boo-boo. I was mixing oil for my boat. The mix ratio for the boat is 50:1. I dumped enough oil for 8 gallons of gas into the tank and filled it, just guessing how much gas it would take. It only took five gallons. I'm guessing that it is a ten gallon tank if memory serves me. So, I have five gallons with the correct 50:1 ratio and five gallons with enough oil for eight gallons of gas. First question, what is my new fuel ratio? Second question, if I drain this fuel and use it in my automobiles, one ounce/5 gal gas (640:1 ratio?), how much fuel should I mix with a gallon of drained boat fuel to get an acceptable/non-harmful mix?

Or perhaps easier, how much more fuel would I have to add to have a correct 50:1 ratio?

 

[otis24]

Supposing I have ten gallons in the tank, I have 1280 ounces of gasoline. 640 ounces mixed correctly and 640 mixed incorrectly.

640 oz fuel ÷ 50 (50:1 ratio)= 12.8 oz oil.

If I mixed enough oil for 8 gallons, that is 1024 ounces of gasoline. 1024÷50 (50:1 ratio)=20.48 ounces of oil. Or 33.28 ounces of oil total.

33.28 oz oil x 50 (50:1 ratio)= 1664 ounces of fuel or 13 gallons of fuel. So, I would need to add three gallons of gas to get a correct 50:1 ratio.

Did I figure this correctly?

 

[ctechbob]

A quick google got me here:

http://www.csgnetwork.com/marineoilfuelcalc.html

8 Gallons at 50:1 gets you 20.48 oz of oil, and
5 Gallons at 50:1 gets you 12.8 oz of oil.

So 33.28 oz of oil in a 10 gallon tank for ~38:1 ratio.

Is the motor that picky that running a tank that rich is going to hurt anything other than make a little more smoke? Not a boat expert but I'd guess not.

 

[otis24]

Well, I did that the hard way, Duh! Since I mixed for 8 gallons of gas and I only added 5, I just need to add 3. Doh!!!!

 

[demarpaint]

Originally Posted by ctechbob
A quick google got me here:

http://www.csgnetwork.com/marineoilfuelcalc.html

8 Gallons at 50:1 gets you 20.48 oz of oil, and
5 Gallons at 50:1 gets you 12.8 oz of oil.

So 33.28 oz of oil in a 10 gallon tank for ~38:1 ratio.

Is the motor that picky that running a tank that rich is going to hurt anything other than make a little more smoke? Not a boat expert but I'd guess not.

If the math is correct, I'd run it down to half a tank and refill it with a 50:1 mix. And slowly over time dilute it that way. I've run, and plenty of people I know have run 2 cycle outboards with a heavier mix than that over the years at one time or another w/o issue. You might see a little more smoke.

 

[FowVay]

Personally I wouldn't mess with it. You added a few extra ounces of oil and brought your mix ratio down to 38:1 (per ctechbob). This certainly isn't going to pose any problems or render any negative impact on anything.

If you go adding straight fuel to the mix you do run a slight risk of reducing the oil ratio if you screw up.

Go run the boat this week and have fun. Pay closer attention next week and get back onto your 50:1 routine at first re-fueling. You might notice that it runs a bit better on the heavier dose of oil so you may decide to bring it down to 40:1 or even 32:1.

Go catch some fish!

 

[Snagglefoot]

I know people who purposely would mix at around 40 to one at the beginning of the season and then dilute to 50 to one . Even on my boat , if I think I need 50 liters of gas, I pour in a liter of oil, then fill the boat with what hopefully will be 50 liters. If it turned out it only took 38 liters, no big deal. Depends on how anal a person is. I find it doesn't cause any sparkplug fouling or starting issues. YRMV.

I would not however, allow the error in the opposite direction.

By the way, working in metric is so much easier, no oz and gallons to work with : just liters.

 

[joekingcorvette]

I would also run it wide open once in a while to keep it from fouling the plugs. In other words try not to idle too much and running wide open will
eat that gas up quickly.

 

[philipp10]

Run it as is, rich in oil. Won't hurt a thing. Don't over think this as everyone here seems to do. You won't foul the plugs. You are at 38
;1....not an issue. If you run out a couple gallons then your good to add just gas and it will be right back at 50:1 (I didn't do the math but it's not that difficult.

 

[Linctex]

Originally Posted by FowVay
You might notice that it runs a bit better on the heavier dose of oil so you may decide to bring it down to 40:1 or even 32:1!


LOL, that was my first thought..... you may like it so much you won't want to go back to 50:1

 

[Chris142]

Many older 2 strokes ran 16:2 and 20:1. They didn't foul plugs. Go use your boat and don't think about it.

 

[Elkins45]

Add my vote to the "just run it" tally.

I can't even begin to calculate how many gallons of 16:1 went through my grandma's old Lawn Boy and that thing ended it's life with the same spark plug it started with.

My dad had one can of two stroke gas mixed 32:1 and every engine he owned got fed from the same can regardless of what it was supposed to get. If he ever fouled or burned an engine I'm not aware of it.