I have a 1977 Mercury 200 (20hp) with a very rough idle. I have new plugs, and the carbs were rebuilt this winter. I have fresh gas.<br /><br />I am not sure if this is a carb problem or a timing problem.<br /><br />It seems to have more vibration in gear than in neutral. However at WOT it runs like a scalded dog. Once you get over 1/3 to half throttle it smooths out and runs great.<br /><br />I have tried to make some carb adjustments with muffs on and the motor in gear. Is this the same as making them on the water?<br /><br />Any tips and tricks for this old motor would be greatly appreciated.<br /><br />Robert
