My grandfather and I just purchased an old evinrude for our little john boat and we replaced the fuel lines and spark plugs are in good shape. We replaced the fuel as well and tried to clean out the carb and that was able to get the outboard to start but it never stays on for more than 15 seconds. It smells like it is burning really rich and I cant figure out how to properly adjust the two Hi/Low speed knobs to hopefully keep it idling. Any assistance on something we are missing our how to remedy this issue would be greatly appreciated.