old outboard oil recommendation

[foresthawk]

I have just gotten running a Sears 7hp. air-cooled outboard. Single cylinder.
I used 16/1 just to get it going, but what would be the recommended gas/oil ratio to use having no owners manual? Seems 16/1 probably unnecessarily oil rich, but don't know.
This motor looks to be something from about 1965-75 by appearance. Model no. is 217 - 58531.
By the way, runs very well on the motor stand.
Thanks for any and all info.

 

[lars11]

Don't know this particular engine, but I have never used more than 4% oil i twostrokes, from 70s and forward. Heard of 5% but not used myself. 6,25%? sounds tacky/sooty.

 

[cmhj]

Back in the late 60s we did use a 16:1 mix. The air cooled Techumseh's, which this is if memory serves ran hot. If it happens to be a Clinton power head same applies.

Keep in mind the differences in oil from then to the mid 80s and now.

Once we had decent oil a 25:1 mix or so is where we ran most of our old air cooled outboards after the mid 80s air cooled oils came out.

 

[foresthawk]

Would it be of any benefit to run a modern air-cooled oil in this motor such as Mobil 2T or any other ISO-LEGD/JASO FC rated oil?

 

[Steve S]

I would try to find the factory recommended ratio .

 

[dwendt44]

25:1 would likely work OK.
Using good brand oil, of course.