Say I hope this helps someone looking to adjust for high altitude.
To get perhaps a slight amount of power back and to reduce excess smoking and fuel use and engine bogging if still set to sea level from the factory.
Here I've attached some of the pages from the high altitude OMC 2217 bulletin people refer to look at. It doesn't seem to readily available...
The only pages I have that someone shared a few years ago for my 1980 CS 140 Evinrude. The intermediate in mine (probably from the factory) is 29M.
My low-idle jets have air passing through them to control the air fuel mixture. This is why larger jet sizes for my low circuit actually leans the fuel mixture.
Some say that the ethanol in our modern gas makes it slightly leaner.
If true, I suppose perhaps this chart's recommended jet sizes should be adjusted by one size for our 10% ethanol gas.
I live at 6,000 ft and use my boat at 5,000 ft. I bought the orifice-jets I needed on e-bay for about $6 each.
Don't go too lean or for the idle circuit, you'll get the idle lean sneezing and for the high circuit you could burn up your pistons-ruin engine.
Oddly, no-one seems to recommend increasing the timing advance by 1/2+ a degree for every 1,000 feet elevation for high altitude like they do for 4 cycle engines. Evidently it's hard to tell with these 2 cycles if they are set too high experiencing knocking till it's too late and the engine is damaged. It kind of scares me that these engines rev so high at full speed. I'm just happy to have rejetted to reduce excess smoking and fumes.
Take care and let's keep our old 2 cycle running respectably!
Jim
