Re: Merc 40hp Idle adjust
You removed the idle mixture screws without determining where they were set didn't you! Start with the screws adjusted about 2 turns out from lightly seated. Then start the engine. Adjust the top carb by turning the screw in in 1/8 increments, pausing for 15 - 20 seconds to allow the engine to respond. Continue until the engine begins to bog. Note the position. Then turn the other way until the engine bogs. Happiness is somewhere between those two settings. Repeat for the other carb(s). Adjust the idle speed up or down to spec after each adjustment. If the engine bogs when you go full throttle from a stop, you may have to richen the mixture a bit to achieve smooth transition. A service manual for your engine would contain the instructions and other tune up related info.
