fuel to oil ratio

J

JBK248

Seaman Apprentice
Joined
May 5, 2012
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42
I recently purchased a used Yamaha outboard and also tracked down a service manual for it. The manual calls for 100-1 fuel to oil ratio. I am hesitant to go that lean. Should I be ? I was considering 50-1. Do any of you run 100-1? Looking for some recommendations thanks. ( Its a 1984 25hp )
 
gm280

gm280

Supreme Mariner
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Jun 26, 2011
Messages
14,592
Re: fuel to oil ratio

WOW that is lean on the oil I'd say. I personally would run a 50:1 and see what happens. Better to be on the oily side then burn up an engine. If problems surface with 50:1, you can always revert to the 100:1 mixture...but I wouldn't...
 
Silvertip

Silvertip

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Sep 22, 2003
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28,762
Re: fuel to oil ratio

Yamaha outboard doesn't tell us much. What engine, what year? OMC had a 100:1 ratio at one time but quickly recommended going back to 50:1. I wouldn't run it at that ratio. 50:1 will not hurt anything other than possibly createing a little more smoke. However using a semi- or full-synthetic oil will help in that regard.
 
J

JBK248

Seaman Apprentice
Joined
May 5, 2012
Messages
42
Re: fuel to oil ratio

thanks for the input. model is 25eln.
is mystic brand oil any good?
 
C

colbyt

Master Chief Petty Officer
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Aug 9, 2012
Messages
824
Re: fuel to oil ratio

I suspect that 100-1 names a specific brand of oil. Be sure to check that.

Consensus of what I have read and what I would do if it were mine I would follow Silvertip's advice and try it with 50-1
 
C

Capt Ken

Commander
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Jul 30, 2002
Messages
2,269
Re: fuel to oil ratio

You will be be fine with the 100:1 mixture. Less coking of the cylinders is the reason. The carb is jetted for that mixture and running heavier oil can cause the engine to run leaner.
 
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