Home › Forum › Ask A Member › air cover on ’68 Johnson 20hp – needed? › Re: air cover on ’68 Johnson 20hp – needed?
OK, well I am not quite sure what the correct initial needle adjustment is supposed to be for a 68 20hp. I am "assuming" it is 1.5 turns, but need confirmation. So, how far out is your needle set when it idles OK? When you say the engine blubbers at midrange, again I am assuming it is running rich/rough, not sneezing. Are you sure you have the carb pick up set properly? Perhaps try advancing the pick up just slightly to see if that helps, but the throttle plate MUST be completely closed at idle.
The air silencer wouldn’t have much of an effect at dead idle, but it sure could have an effect at midrange. So, I would reinstall it and try again before going much further (sorry should have suggested this first).
But again, these engines are surely cold blooded, so they are bound to idle poorly and not warm up sufficiently in the cold weather we are still having. You might try plugging the water bypass around the thermostat temporarily to see if the helps idle performance in the cold weather. If so, the engine will probably idle OK in normal summer temps, and you can remove the temporary bypass plug.