Re: 1960 Evinrude Fastwin idle screw on shift handle questions.
HI tom. Yes, there is an approximate setting(s). Here are some great links that can explain it in detail. Once you have the idle dialed in, be sure to snug down the little brass nut the needle passes through. You'll also want to run 24:1 mix with Champion J6C spark plugs.
http://forums.iboats.com/engine-fre...sorted-carb-variations-joe-reeves-167352.html
Maintaining Johnson E & FD Serie
EDIT: Just for clarification, are your referring to the carb idle needles, or the white, nylon idle stop located at the back of the tiller handle? If it's the idle stop on the handle, it is used to advance/retard the timing. Turning it in advances the spark and raises the rpms slightly. Conversely backing it out, retards the spark and lowers the rpm. The idea is to use idle adjust needles on the carb to dial in the best fuel to air ratio, while using the idle stop screw to find the best rate of spark for idle. If mostly just take trial and error, but you can actually remove the screw altogether. By doing so, you can kill the motor simply by turning the throttle to the STOP position, however most folks like to use the nylon screw to adjust the idles such that they can turn it all the way down, while in gear, and just barely keep idling.