3hp carburetors

[stanley]

How was Johnson/Evinrude able to change from high speed adjustable to fixed high speed jets on the 3hp motors?The change apparently happened late 50’s early60’s?Lookimg at two last night,they seemed to be the same except for that one feature.

[dan-in-tn]

The change appeas to have happened between 1962 (JW-17) & 1963 (JW-18). Looks like just the needle was done away with & a non adjustable orifice was installed that the engineers felt was the optimal tune? Many like to tune their own motors for varying conditions. There was a kit made to put a needle back in motors for tuning purposes (high altitude) that you can still find today for different size motors. The needle just doesn’t stick out the front of the cowling. Takes a small screwdriver to adjust it. Hope that is what you had in mind.

Dan in TN

[outbdnut2]

Elimination the hi-speed adjustment was done on a lot of motors back then. Probably a combination of cost reduction and eliminating problems of people who just don’t get it when they have to adjust the hi-speed jet.

Note that somewhere in the 1990s, the federal gov’t mandated the hi speed adjustment go away in most gas engines to keep people from getting them running to rich and polluting the air. I tried to buy conversion parts or a whole new carb for my son’s snow-blower (Techumseh engine) because it was running too lean and was told it was against the law to sell such things. I drilled out the main metering jet one numbered drill size bigger to get it to run right.
Dave

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