Gas/Oil Leak?

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JGibson

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Been noticing some oily residue behind me when I'm idling or just after I shut off the engine. I don't see anything inside the motor housing to suggest it is leaking...only thing I can see is some older looking grease or oil residue below the housing, could this be what I'm seeing? The motor is my 1968 20hp Johnson. I'm not seeing any loss of gas from the tank other than regular running. I had a full tank (6gal) and ran it the last 3 days ending up with about 3gal left...????
 
Older two strokes are notorious for that, at least mine did it frequently. Unburnt oil/fuel coming from the exhaust. How are you mixing your gas? Think the old motors were 100:1 though I'm not sure what years?? When I ran my 50's OMC I did 100:1. None the less it's better to be safe than sorry.
 
To re-visit a recent thread. I think it's a 50:1 ratio. I was given a Clymers manual when I bought my 68' Evinrude 18hp and that's what the book recommended. I have also noticed an awful lot of oil coming out of my exhaust lately too (the last 2 - 3 trips). It's enough to run down the back of the motor and land on the cavitation plate. When I bought the motor it was a greasy/oil mess to begin with (figured in the 60's they didn't care too much about the emissions then). I am not too sure if this is normal or not? I do know that sometimes (not always) it idles roughly until it warms up. Gives a knock every 30 seconds or so. Once you give it 1/4 to full throttle though it runs smooth (so it seems). Is this normal for older motors like this?
 
sixgun86 said:
Older two strokes are notorious for that, at least mine did it frequently. Unburnt oil/fuel coming from the exhaust. How are you mixing your gas? Think the old motors were 100:1 though I'm not sure what years?? When I ran my 50's OMC I did 100:1. None the less it's better to be safe than sorry.

That's an excellent way to completely ruin a '50s Johnson or Evinrude! These engines were designed to run on a 24:1 mixture, even with today's oils. There is no carbureted OMC engine that should be run on 100:1 at all. The ones that were originally designated for this mixture were changed back to a 50:1 mixture via dealer and customer mailings plus a service bulletin.
To answer the original question - starting in 1964 the mixture was changed from 24:1 to 50:1 on OMC product.
 

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