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fuel/oil ratio question

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  • fuel/oil ratio question

    does anyone know the gas/oil ratio for my 69 Boa Ski 19 hp Hirth engine, for some reason 50:1 comes to mind but it's been a long time and i'm not sure, and I wanna try and fire up the ole girl today using a hose into a gas can just to hear it run again
    Last edited by Boa Man; 04-15-2018, 11:04 AM.

  • #2
    50:1 with modern oil and good premium non ethanol fuel will be fine.

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    • #3
      cool thanks I've got a can of VP premixed 50:1 they say it has no ethanol so i'll give it a go

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      • #4
        I agree. I run a premium oil with non ethanol fuel ( shell vpower) . Today's high quality synthetic oils allow you to run leaner with full protection. 50:1 with today's oil is like 20:1 or 30:1 with the old oils from the seventies.
        Ray

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        • #5
          I read somewhere last night that back in the day a lot of people used a 20:1 ratio

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          • #6
            The 71 Boa Ski operating manual states: "For the first 10 hours the gasoline-oil ratio should be 20:1, (20 parts gasoline to 1 part oil): thereafter 25:1." If you rebuilt the engine, lots of guys including myself run a ratio closer to the manufacturer spec for the first tank. I personally run 40:1 for my Hirth engines on a day to day basis using an ordinary name brand two stroke oil. Word of caution, my Diablo friends are saying they are burning out pistons in their Hirths with the 40:1 ratio using synthetics and have gone back to a richer mixture. Just saying...

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            • #7
              Our first 69 MS capri had directions for mixing with SAE30 oil ... @20:1
              We used Wynns @ 40:1 in our MS18 for three of its years and were glad to not have to change any more plugs and
              discovered the JLO396 in it was still pulling fish huts on Lake Simcoe into the 80's .
              Ron

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              • #8
                Originally posted by BB16 View Post
                The 71 Boa Ski operating manual states: "For the first 10 hours the gasoline-oil ratio should be 20:1, (20 parts gasoline to 1 part oil): thereafter 25:1." If you rebuilt the engine, lots of guys including myself run a ratio closer to the manufacturer spec for the first tank. I personally run 40:1 for my Hirth engines on a day to day basis using an ordinary name brand two stroke oil. Word of caution, my Diablo friends are saying they are burning out pistons in their Hirths with the 40:1 ratio using synthetics and have gone back to a richer mixture. Just saying...

                good to know thanks i'm glad I did not start it yet, most certainly I would rather change a plug or two then then damage the engine

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                • #9
                  Originally posted by RON HYDRAULIC YAM View Post
                  Our first 69 MS capri had directions for mixing with SAE30 oil ... @20:1
                  We used Wynns @ 40:1 in our MS18 for three of its years and were glad to not have to change any more plugs and
                  discovered the JLO396 in it was still pulling fish huts on Lake Simcoe into the 80's .
                  Ron
                  nice nice

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