Gas/Oil mixing

[JSMoore]

I have a 1997, Evinrude 90 Special, that requires that you manually mix the oil into the gas. The boat has a belly tank under the floor with a fill port and vent on the outside of the boat.

Since I've never had a motor before that you do that, I got to thinking....... If the tank has some fuel in it already and you fill it up, you obviously add a certain quantity of oil, depending on how much "new" gas you've added. So, if you filled the tank, how do you add oil if the tank is already full?

The obvious answer is, don't fill the tank all the way full. But, I can't see the tank. So, I don't know it's full until a little squirts out the vent/overflow. Hmmmmmm........ Any help here?
Thanks!
JSMoore

 

[leesumm]

Re: Gas/Oil mixing

I would have to ask first, you don't have a fuel gauge ?

 

[rockyrude]

Re: Gas/Oil mixing

You could add oil in steps, 10 gal , oil for 10 gal. Add more gas, add more oil and so on.

 

[Chris1956]

Re: Gas/Oil mixing

If fuel squirts out the overflow, it is near to full. Sounds like you need to siphon it dry and start again.

 

[emoney]

Re: Gas/Oil mixing

Instead of forcing every last little drop of gas into the tank, stop pumping as soon as it kicks off the pump-full. Then, the amount of oil you're adding will have plenty room to fit in there. If you're adding something like 100 gallons, then I'd do as rockyrude suggested and add it in steps.

I went through this same dilemna the first time I filled up a pre-mix fuel tank, but when I let the gas settle, I realized it had room because in proportion, you're not adding that much in terms of volume of oil.

Plus, I like to stop at even numbers in terms of gallons. It's a lot easier to do the math when you stop at 10, 20, etc. gallons than if you go to "full" and have to figure out how much oil goes into 14.67 gallons of gas. They'll still be selling it if you run out.

 

[JSMoore]

Re: Gas/Oil mixing

Thanks for the suggestions.

emoney - If I do as you suggest, and I pump 10 gallons into my 37 gallon tank before it "clicks off", that would mean I would have to add 25.6 oz, or close to a quart of 2-cycle oil. Are you saying that I should have enough room to pour that in AFTER the pump "clicks off"?
Thanks!
JSMoore

 

[Tim Frank]

Re: Gas/Oil mixing

You should really mix before you fill....otherwise you don't necessarily get uniform mixing if you just throw some oil in with the gas.
Are you filling from a fuel hose or jerrycans?

 

[sschefer]

Re: Gas/Oil mixing

If you know how much gas it took to fill it and are sure the fuel in it was already mixed gas then all you need to do is siphon off about a gallon and add 2.6 ounces of oil for every gallon you added. Don't worry about it mixing, it will mix just fine but if you're skeptical, just tow the boat around the block a couple of times. The sloshing will mix it for you.

 

[Silvertip]

Re: Gas/Oil mixing

A 50:1 mix is one pint of oil to six gallons of fuel. If you can remember 6, 12, 18, 24, 30, 36 etc., then all you need to do is pump 6, add 1 pt., add 6, add one pint, repeat until near full. Add 3 and add 1/2 pint. Or if the tank is nearly empty, pump 12 and add 1 qt. Pump 12 and add 1 qt. See how difficult you are making a simple situation?

 

[JB]

Re: Gas/Oil mixing

If in doubt, add oil. Oiling an outboard is like watering a horse; more than is needed (even twice as much as needed) is not harmful, but less than is needed may be fatal.

 

[JSMoore]

Re: Gas/Oil mixing

Thanks, guys. Like a lot of things, everybody's got their own ideas. Good to hear them! I'll "get 'er done".
Cheers!
JSMoore

 

[leesumm]

Re: Gas/Oil mixing

I posted this on another post some where , but if someone needs a good calculator for the gas/oil mix, this seems to work for me, just put in the correct numbers and calculate http://www.csgnetwork.com/marineoilfuelcalc.html