We just purchased a 2001 13 ft Sport Boston Whaler with a 2001 Mercury 40 hp 2 stroke(2 cylinder with a single carb). Listening to the exhaust note, I can hear a miss that is more noticable at idle, but is still there even through mid range. Idle speed in gear is 850 rpm and about 1100 in neutral. If you try and set the in gear idle speed to 750 rpm it tends to quit. The motor also shakes a bit in gear and at idle but smooths out as power is applied. I have cleaned the carb, set the oil injection, put in new plugs, changed the gas and oil, and played with the air mixture with no avail. Compression was 125 in each cylinder. there is not much time on it. The engine does not bog and runs right up to 5500 rpm. The motor is still under extended warranty so I brought it in to the local Mercury repair shop. He set the timing and adjusted everything but it still sounds the same. He mentioned this is just how the 2 strokes run. Is this true? My 6 hp on our canoen idles smooth with no noticible missing sound. Is it just the bigger outboards that do this or is it the 2 cylinder, 1 carb, setup? Could it be something in the CDI ignition like low voltage or bad coil? We just bought the boat and the original owner thought it was running a bit more rough since he put it away. Any help would be greatly appreciated. Thank you......
