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Discussion Starter · #1 ·
I have an older Evinurude ('57 18HP) that has a recommended fuel mixture of 24-1. I have spoken to West Marine and they told me that with older outboards that have "loosened up" that I could run a leaner mixture of 50-1. Has anyone had any experience with this? I would like to reduce the plug fouling and "smokey joe" that comes with 24-1 but don't want to kill my engine.

On a similar topic has anyone had any experience using synthetic 2 cycle oil in outboards where you mix the oil and fuel? I know that synthetic is biodegradable and would just like to sooth my conscience when running my outboard by at least making an effort to reduce the impact of the pollution it creates. Is it possible to mix synthetic in a tank or does it require a direct injection of the oil at the engine?
 

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I had a 1957 7.5 hp Johnson Seahorse. I asked two boat mechanics and received different answers. One said it was ok to run a leaner mix and the other said absolutely to not run leaner than 24:1.

I ended up compromising and ran 40:1. I had the motor for two years and never had a problem. And I noticed a huge improvement when trolling. I could troll slower and for longer before burning off the plugs.
 

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Most of the newer motors run at 50:1. If your running the synthetic you should have longer plug life. I have run older motors at 50:1 with no problems.
 

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I had a 55- 25hp Johnson Seahorse. I checked with several OB mechanics and the general consensus was that 48-1 is perfectly ok. Mainly because the technology of lubricants has advanced so much since the motors were maunfactured ie: I have an old tech manual for the 1950's Johnsons and they recomended a 24/1 mix of 30wt motor oil !! I'd go with 48/1 with a good outboard mix oil, you'll be fine.
 

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Eric,
I run a 50:1 mixture (mfg recomended mixture) of Amsoil symthetic in my 2-cycle 1986 8hp Merc kicker on my DB and have had no problems, not even any plug fouling at all.

JK
 
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