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High Altitude problem

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c canada

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"I have a 1984 15 HP Johnson m

"I have a 1984 15 HP Johnson motor that idles really good and will run 20 mph top end in the Dallas Tx area (600 feet altitude). I like to fish in Colorado around 8500 to 9000 feet above sea level. With a small low-speed adjustment, the engine still idles really good at the altitude of 9000 feet but only goes 9 mph top end. Is there a high speed jet for higher altitudes or a carburetor adjustment that I can make on my engine for higher altitudes?"
 
You will have to get a smaller

You will have to get a smaller main jet AND lower pitch propeller! At that altitude you loose about 15% power whatever you do.
 
"The carburetor kits sold here

"The carburetor kits sold here (and other web sites) seem to have standard parts and no choices on the main jet size. Any suggestions on the main jet size, and, where I could find them?
I asked about jet and float adjustments - Are there any other modifications/adjustments possible that might help the high speed of this engine?"
 
"In this case You may have to

"In this case You may have to find a Johnson/Evinrude dealer. In the original workshop manuals there are lists of all jet sizes and types with part numbers.There are no high altitude kits available, this is more of an try-fail operation. Bring the old main jet -the number is stamped on it and go down a couple of units."
 
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