Re: 1960 Johnson RDS-22 40HP
There are two needle/gas adjustments on your carb, each should have a knob. The one up top is the slow-speed idle circuit adjustment, the one below is the high-speed adjustment. Turn both clockwise gently until they stop, don't force them. Back the high-speed/bottom needle out (counterclockwise) 3/4 of one full, 360-degree turn. Back the slow-speed needle out 1 and 1/2 turns. Put it in a barrel of water or take it to the lake and back the trailer down like you're going to launch...make sure the leg of the motor is well submerged. Start it up and let it warm up. Run the throttle up a little and adjust the high-speed/bottom jet a little either way until it runs really well. Sound like yours is running rich...too much gas. My old Evinrude Big Twin 35 hp 1957 runs best at about 3/8ths of a turn out. Turning the knobs clockwise leans/lessens the gas, turning counterclockwise richens/adds gas. After you get the bottom needle adjusted, throttle it down to idle and adjust that needle the same way...get it idling smooth. You'll have to tweak these a little out on the water, and remember...a little rich is a good thing. In other words, after you find the sweet spot in each adjustment, richen the mix a little so the motor doesn't starve for fuel. Your motor has a rev-limiter that won't allow you to run it up to WOT in neutral...you can only get that in gear. Don't run it out of the water, even on the mufffs...you'll fry the impeller. Also not good to throw it in gear and rev it up in that situation. Good luck and post back with the results.