Yes. My mistake. Thanks for pointing that out.
That is why they chartered two steam tugs and put extra boats on Powhatan.
Not according to Porter. He said that all the little boats on the Powhatan were unserviceable. He said none of them were useable. He makes no mention of any "new" boats being put on the Powhatan.
May be wrong about the extra boats on Powhatan. But the plan never called for the supply ship or the warships to enter Charleston Harbor. They were to be anchored about 4 miles from Sumter. That would have put the ships beyond the range of the Confederate gun batteries. The tugs and small boat would come within about 1200 yards of those batteries and have been well within their range.