Fuel Mixture problem, need help

[SnohoBassGuy]

Guys, I just purchased a 1961 5.5 Evinrude outboard. My problem is that my tank is about half full of 50:1 mixture, and this new motor needs 25:1.

What would be the best/safest way to change the mixture. Obviously I need to double the oil added, but I cant really tell how much is in the tank. Would it hurt to just make an educated guess?

I'm fishing tomorrow, so any help would be great!

Thank you.

[Big D]

I would fill the tank with new fuel and remember how much you put in. Subtract the amount of new fuel from the total amount that the tank holds and that will tell you the amount of old fuel you had in the tank to start with. Then you should be able to figure the amount of oil you will need to add,
Good luck!

[Anglinarcher]

And if you think you might error, error on the side of too much oil. The engine may smoke a bit, but too much oil will not hurt it, while too little sure will.

[saltyseadog]

could you dump or pump the tank and start over at 25 ta 1?:-k

[G-Man]

I think you'll find that today's 2-cycle mix is a great improvement over what was available back in 1961. In fact, if I'm not mistaken, the instructions on the engine cover say to use 30 weight oil at 25 to 1. Whatever you do, don't use today's motor oils. It's formulated not ot burn or breakdown and will pollute the waters in which you run. I have a vintage 50's 3hp Johnson with the same mix instructions that happily runs using a bio-degradable and fully synthetic oil, XD-100, at 50 to 1. It's the same stuff that I run in my e-tec, it burns nicely and I feel better knowing that if any makes it into the environment it will breakdown quickly. You should be able to run with any TC-W3 compliant oil at 50 to 1 without any problems. So if your tank is half full and you used a good modern 2 cycle oil, I'd just run with it.

[BassFanatic]

G-man is right just run it, If it smokes allot let it burn off and see what happens, If the problem still exists, drain it and start from scratch. hit me on a pm if you have anymore troubles.

[BentRod]

I'm with G-man too. I've got a '78 evinrude 4hp. However it is a 50:1. Not knowing anything about outboards when I gotit, I've done a lot of research since and come to some of the same conclusions that G-man stated. One big one is that vintage 2-stroke oil is nothing like the modern 2-stroke oil. You can try contacting your local marine repair shop and get some free advice or info. I have talked to/gotten parts from Eastside Equipment and Marine in Issaquah. There is also a good Evinrude outboard forum on iboats.com.
Have fun with it. Hope your fishing trip was successful.

[Rich McVey]

I hafta say, when I got my 1969 Johnson 55, I dint know what the mixture in the tank was. Started from scratch in a 5 gallon gas can, and just filled up the boats tank. I didnt have any issues with smoke once the motor warmed up.

[SnohoBassGuy]

I'm with G-man too. I've got a '78 evinrude 4hp. However it is a 50:1. Not knowing anything about outboards when I gotit, I've done a lot of research since and come to some of the same conclusions that G-man stated. One big one is that vintage 2-stroke oil is nothing like the modern 2-stroke oil. You can try contacting your local marine repair shop and get some free advice or info. I have talked to/gotten parts from Eastside Equipment and Marine in Issaquah. There is also a good Evinrude outboard forum on iboats.com.
Have fun with it. Hope your fishing trip was successful.

Thats funny because my other motor is that same one.

as for dumping out the tank, why would I want to do that lol

I think I will take Big D's advice and fill her up and then subtract the remainder.

Appreciate the advice. Unfortunately I wasnt able to get out the next day (got hurt), but will be going this Sunday.

[BassCaster]

New, old motor? Mix in some SEA FOAM, it has worked wonders for me, boat, motorcycle, you name it.