almost always 50 to 1. then i add an extra spalsh since i run the piss out of my 6 horse evenrude maybe try going a bit less so i dont smoke for hours trolling. i use the evenrude mix oil since i seen it on the shelf and i have an evenrude. get one of those measuring things it helps you get the right mix rather than guessing everytime and getting different results.
I have a '63 3hp Johnson. I run 50:1 in it to the best results. I can adjust my fuel/air mix for both low and high engine speed, so I do not stray from the base mix to control smoke. I can troll down to an absolute crawl for hours on end and trim the mix down enough to keep it from smoking me out.
The older motors (and smaller) are not as temperamental as the new ones for the oil. The new ones (I think) have jeweled bearings and are set up for a thinner mix to reduce pollutants. The bearings are very intolerant of low oil levels and the motors will foul plugs if too much. So, you really can't screw with the mix. But the older ones, I have been known to just add gas to the tank in a pinch without adding oil, effectively cutting the ration in half and all I do for insurance is fatten the air/fuel mix. Not the best thing to do, but when it is 4 am and you are sittin' at the launch with a boat full of decoys and you realize you don't have enough fuel, you siphon from your truck and bite the bullet.
God bless those old smoke chuggers.
Oh, and go get yourself some RV fuel stabilizer (can't remember the name of the stuff but it is blue and I get it from my Yamaha dealer). It is the only stuff I know that protects the engine from the ethanol in the fuel now. Stabil (last time I checked) does not. This stuff will keep fuel fresh indefinitely.