crappyfisherman Posted July 21, 2011 Report Share Posted July 21, 2011 any one know what ratio i should be using with my mid 70's "500 Mercury"? ive been told 50-1 but would like to know forsure, keep the old girl happy. thanks Link to comment Share on other sites More sharing options...
GBW Posted July 21, 2011 Report Share Posted July 21, 2011 I too run 50:1 in my 70's Jhonson unit. (easy there all you smart reading... ) Link to comment Share on other sites More sharing options...
Fish Farmer Posted July 21, 2011 Report Share Posted July 21, 2011 Id say 50-1 also, I know when I had my 1961 10HP Evinrude they didn't have 50 to 1 oil, we used 1 Quart of 30 sae regular to 5 GALLONS of gas. Link to comment Share on other sites More sharing options...
crappyfisherman Posted July 21, 2011 Author Report Share Posted July 21, 2011 thanks fellas. makes me feel better knowing im not hurting it. Cheers! Link to comment Share on other sites More sharing options...
GBW Posted July 21, 2011 Report Share Posted July 21, 2011 if you can, find out the brand of oil the last owner used. you might not want to start running AMS-OIL Synthetic in it if it's never had it run through it before. If you cannot find out, run the good old style stuff you can get at CTC as that's what was more then likely used in the past. Just my extra to the reply... Link to comment Share on other sites More sharing options...
tightline Posted July 21, 2011 Report Share Posted July 21, 2011 definetley 50:1 my buddy has 2 and we run it all the time Link to comment Share on other sites More sharing options...
backbay Posted July 21, 2011 Report Share Posted July 21, 2011 The design of the oil dictates the ratio: not the engine itself. Just follow the directions on the container, that'll keep you out of trouble. Link to comment Share on other sites More sharing options...
Uncle Buck Posted July 21, 2011 Report Share Posted July 21, 2011 i always run my older motors at 45:1... a little extra just to be safe... cheaper then changing engines... Link to comment Share on other sites More sharing options...
Billy Bob Posted July 21, 2011 Report Share Posted July 21, 2011 I bought a new 1975 7.5 hp Mercury back in 1975 and it was 50:1 on the oil. And no it's not what kind of oil you use but what the manufacture recommends that determines the ratio. Bob Link to comment Share on other sites More sharing options...
bubbles Posted July 21, 2011 Report Share Posted July 21, 2011 I have that motor, 50:1 Link to comment Share on other sites More sharing options...
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