1989 Evinrude 15 hp question?

I got a 1989 evinrude 15hp 2 stroke outboard motor and I was wondering what the best octane of gasoline to use when premixing 50:1 oil ratio and keep in mind I live in California famous for its oxygenated gasoline. Also how come an evinrude is more reliable then a 1989-1991 mercury 15m 2 stroke from what I hear the

I got a 1989 evinrude 15hp 2 stroke outboard motor and I was wondering what the best octane of gasoline to use when premixing 50:1 oil ratio and keep in mind I live in California famous for its oxygenated gasoline. Also how come an evinrude is more reliable then a 1989-1991 mercury 15m 2 stroke from what I hear the evinrude is also slower then the mercury 15m how come the mercury of the same horse power is faster then the evinrude by 3 mph? here are the top speed test for both motors links https://www.youtube.com/watch?v=Kdu9vf4br80, https://www.youtube.com/watch?v=7irSPoEZ_Mw

Best Answer:

Vlad: Regular 87 is fine. The Mercury outperforms the Evinrude because Mercury has always underrated their motors, so that they would win all the races. If the Merc says 15 HP, it's about 18.

Other answer:

Vlad:
There was 2 mph difference (23 vs. 25). But they were on different boats which may have somewhat different weight or drag. And it may depend upon which way the wind is blowing. Also there are different prop pitches available which to handle heavier (more thrust at lower speed) or lighter (lower thrust at higher speed) boats.

I had an older 15 hp Evinrude on a streamlined duck boat and it would do 25 mph. So do not put too much faith in a minor difference between different motors on different boats.

Before unleaded gas for cars, unleaded white gas used for boats was 80 octane. No outboard should have any problem running 87 octane unleaded regular. My dad was an engineer at OMC (parent company of Evinrude, Johnson, Lawnboy, Cushman, etc. at the time).

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Also there are different prop pitches available which to handle heavier (more thrust at lower speed) or lighter (lower thrust at higher speed) boats.
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So do not put too much faith in a minor difference between different motors on different boats.
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the older 15 hp developes its hp at 6000 rpms make sure you have the right prop on it. verify it with a tachometer
Shaun H-A:
87 octane is just fine for it.