Re: 74 Evinrude Carb Question
If it has a lot of play in it, then yes a worn throttle shaft can cause low-speed and idle problems. I've seen it many times on the vintage sled motors I work on (Mostly Tillotson and Walbro carbs...very similar to the carbs used on your engine). Basically it'll run lean at idle, giving it sneezing or dying problems. As the engine vibrates, the shaft jiggles around and causes a variable air leak that can be darn near impossible to tune out.
Take a can of carb cleaner and spray the outside of the carb where the shaft goes through the body. If you hear a change in RPM or tone, then it's leaking enough to cause problems.
No, your carb doesn't have shaft bushings, but if you have a good machine shop in your area they can probably fix it for you by drilling the carb body and installing some bronze bushings. Hopefully the brass throttle shaft isn't worn too badly, they are trickier to repair. You'll need to braze some material to build it up and then turn it down to the original size on a lathe. Not real hard to do but requires a gentle hand and you can warp the shaft when brazing it so you might have to spend some time truing it up afterwards.
One particularly rare Tillotson I rebuilt, the shaft was worn so bad I had to make a new one. Did the replacement out of stainless rod. That rebuild will outlast me.
Once that's done, that carb will be good for much longer than the 23 years it's gone so far.
