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What was logic of a 100:1 fuel mixture on a late 80's Evinrude 15hp

S

Snapper Fisho

Regular Contributor
Hi, does anyone know why the factory specs, as in the attached pic, for a late 80's Evinrude 15hp Rope Start was 100:1?

Has been run like this for years but still shows about 95-100psi in each of the two cylinders cold after 3-4 pulls.
 

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  • Factory Evinrude 15hp Fuel Ratio.jpg
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I am going to say the the board room decided this !!!-----Loosing market share because the general public believes that a 100:1 motor must be " better built "-------So suddenly / overnight an identical motor can now run with 1/2 the oil.-----It was a mistake.-----Many folks now realizing how good and how long these 9.9 / 15 HP will run.-----Run that motor at 50:1 as per the service bulletin that came out to go back to 50:1 on these.-----Just more proof that 2 strokes and the concept of lubrication in them is not well understood.
 
Thanks racerone. Really respect your brilliant knowledge here and also Joe's. :)

I will run at 50:1 and I planned to. I didn't know about the service bulletin. It surprised me as the nice older retired man I bought it from has run it at 100:1 all these years (no-one told him either at the service centre to change), yet the powerhead still seems good going by readings I got and the way it runs.

Been looking for a mid 80's 15hp that has the non-cable tiller arm and the full alloy carby with minimal plastic, unlike this one that has. It even has a plastic throttle cam under flywheel that is prone to breaking from what I have read.

However, in Australia hard to find these classic models nowadays and especially one in good condition like this AC model 15hp. So, still happy to get one running well. Cheers
 
I agree-----I would much rather have the non cable tiller arm.----I hate the miniature parts and plastic in the cable tillers.
 
About that 100:1-----because #3 in the industry, Scott-McCulloch, came out with their 100:1 oil first.
 

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Thanks guys. The cable replacement in Australia is for these models where there's more around is about $200 and there are two types. One is around 51cm in length and the other around 97cm. The latter one is unavailable here now.
Lucky we can buy from the States but shipping fee and out government import tax can be hurt lol.
 
My '86 Johnson also had the 100:1 sticker on it when I purchased it used. First thing I did was remove it. Personally, I don't mind a whiff of 2 stroke smoke occasionally. Reminds me of the simpler times when I was very young.
I run my chainsaws, trimmers, etc. at 40:1
 
At 50:1 your grand kids will likely be running that 86 model.-----Hopefully you are installing a new water pump impeller every 5 years.
 
They are brilliant motors for sure. A testament to the fact that this 1988 I have now has been running on 100:1 by first owner for over 30 years and still has a damn good power head!

Sorry about my unclear tiller cable post for these motors but I'm sure you can tell the parts in Australia are a lot more expensive if available. Didn't know there are two types though, one about 51cm and the other 97cm in length.
 
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