100:1 vs 50:1???

Carl

Carl

Moderator
Staff member
My "new" 1985 Evinrude 9.9 has a sticker on the side where the fuel line connects that says 100:1.
I have always run 50:1 in my 2 strokes, from the 115 hp on my old center console, the 1989 9.9 i owned back in 1997-99, my 1999 Nissan 18 that I stupidly sold to get my current boat that had that horrible Merc 25 on it. (I hope the current owner of the Merc is having more luck than I did!)

So, what's the consensus of the DHBP:
Run 100:1 like the factory specs?
Or stick to 50:1??
Or somewhere in the middle???
 
Carl said:
My "new" 1985 Evinrude 9.9 has a sticker on the side where the fuel line connects that says 100:1.
I have always run 50:1 in my 2 strokes, from the 115 hp on my old center console, the 1989 9.9 i owned back in 1997-99, my 1999 Nissan 18 that I stupidly sold to get my current boat that had that horrible Merc 25 on it. (I hope the current owner of the Merc is having more luck than I did!)

So, what's the consensus of the DHBP:
Run 100:1 like the factory specs?
Or stick to 50:1??
Or somewhere in the middle???
Click to expand...
The 100 to one was only instituted to satisfy EPA regulations.

50 to 1 is pretty much the standard and the safest bet for two stroke out boards
 
Stay with 50:1. I had a couple of the 100:1 vintage, they are exactly the same as the prior and following years which specified 50:1. I was never sold on it and always run at 50:1. As Jode said, it was an attempt to satisfy EPA, and claim better oil economy to the consumer. Don't do it.
 
I'll add that as I noted in my other post, my analog compression guage showed 75 pounds in both cylinders.
This is definitely on the low range but these inexpensive gages are notorious for not being calibrated.
I assume that both cylinders being spot on 75 is more important than the actual number???
 
I've had many evinrudes over the years. All new to me motors. Always used 50-1 mix on all. Story, a friend found a 18hp that wouldn't run well, new 100-1 mix. He and the original owner put in a 25-1 mix of oil. Just a little math problem, now that it's all straight the motor is still running,
 
I have a 2009 Yamaha, last year of the 2-stroke. It too came listed as 100:1. I looked at the parts list between my 100:1 and the 50:1 models and could find no differences. All part numbers matched. So I run 50:1 and have no issues.
 
Carl said:
So, what's the consensus of the DHBP:
Run 100:1 like the factory specs?
Or stick to 50:1??
Or somewhere in the middle???
Click to expand...
Lucky you, 1985 was the year Evinrude went to a 100 to 1 fuel ratio. They abandoned that ratio within two or three years.
If I were you, I'd follow their lead and use a 50 to 1 ratio.
I have a 1995 Johnson which is fed 50 to 1. I have a 2008 Yamaha which is fed 100 to 1. The Yamaha does not like a richer mixture. I'm not going to see if the Johnson will survive on the leaner mixture.
You do you on your motor but, it is nice to see you are now storing it vertically. :cool:
 
I ran a ~1990 Yamaha 2 stroke 15 hp for 20+ years after the second owner had run it for at least 15. Pretty sure the original owner's manual said 100:1, not that I ever saw it. I ran at 50:1 with no issues until I ran it onto an unmarked rock at speed and finally killed it. Up untuil then, repeated seasons of using it hard and putting it away wet didn't do any harm that I could discern. It's still in my barn, probably repairable, but instead of spending money on an uncertain and potentially expensive rebuild of the lower unit AND the transom of the 14' boat it came with, I bought a used 4 stroke Suzuki 20 and splurged on a new 16' boat.
 
Never new an Evinrude that old could be set up for 100/1. The 90 ETECH I bought new on my 2072 is set up for 100/1 but you have to use full synthetic oil at that rate. Same motor can be set up for 50/1 using normal 2 stroke oil. Mine was bought new in 2011. Have never had any issues with motor oil related. It sips oil & fuel.
 
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