Most of use have this problem on most pours and we use a wire the size of the spout hole and run it into the spout to clean the lead. Do this with the lead hot of course and be careful. The wire should be bent into a 90 degree with the part that goes into the spout being around 1 1/2'' long and leave a long enough handle to hold onto. You don't have to preheat the pot just turn the heat to high (10) and wait until it get to pouring heat. If your pot is a 10 pound you will not be able to pour big sinkers without having cold spots in the lead. Not enough lead will come out of the spout. You should be able to pour them using a small ladle.
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Ascend 133X 13' - MotorGuide Xi3 & Mercury 4