1991 90 hp Rude Oil/Fuel Mix? Too Rich for 15 yrs?

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whess3298

Cadet
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Jun 14, 2007
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I recently bought a boat with a 91 Evinrude 90 hp motor. The previous owner said he always mixed at 32:1. He had the boat for 14 years. Isn't this too rich? It runs smoothly and idles well, but I am not getting the wot rpms that I should. . .can only get 4500 - 4800 rpms. Should I start mixing 50:1? The boat was in Texas for last 15 years, I now have it in Colorado at 5100 ft elevation. Please help!
 
WillyBWright

WillyBWright

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Dec 29, 2003
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Re: 1991 90 hp Rude Oil/Fuel Mix? Too Rich for 15 yrs?

You're going to need a lower pitch prop and different carb jets at that elevation. Seek out a local dealer. They'll be well versed in the idiosyncracies of high elevation outboards. 50:1 is the correct ratio. What elevation was it at? Dallas is pretty low. Flagstaff is pretty high. Wikipedia the location.
 
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whess3298

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Joined
Jun 14, 2007
Messages
9
Re: 1991 90 hp Rude Oil/Fuel Mix? Too Rich for 15 yrs?

The boat was around Dallas - low elevation. I am running a 13 3/8 X 17 prop now. Will I need to go to a 15 pitch? The motor seems to run smooth and idle great so far here at 5000 feet. I asked the dealer if I needed to rejet. . .they just said they recommended not doing it unless absolutely necessary. Thanks for your input.....
 
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whess3298

Cadet
Joined
Jun 14, 2007
Messages
9
Re: 1991 90 hp Rude Oil/Fuel Mix? Too Rich for 15 yrs?

Thanks for the post. I did a decarb. . . I am going to try the 50:1 mix tomorrow and am going to get a 15 pitch prop soon.
 
kenmyfam

kenmyfam

Supreme Mariner
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Aug 10, 2006
Messages
14,392
Re: 1991 90 hp Rude Oil/Fuel Mix? Too Rich for 15 yrs?

The only thing a richer mix will do is foul up plugs and exhaust quicker in the way of damage. De-coke will take care of that. You have a much better situation than having too lean a mix.
 
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