I have long held the belief that the CSS Ponchartrain was concidered more of a threat by the Union Navy in 1863 than modern historians give her credit for being. The fact that the true nature of her condition was fully discovered when the Union Army finally took Little Rock on September 10th of 1863, doesn't detract (in my opinion) from what the Union Navy appears to have thought of her prior to that time.
I think they feared her potential of being another CSS Arkansas and cutting their supply lines on the Mississippi between Memphis and Vicksburg. There were at least 2 of her original heavy Guns left in Arkansas, also captured in the Little Rock Arsenal in September 1863, to rearm her with should she have become operational as an Ironclad. They had been used as the main battery at Fort Pleasent guarding the Arkansas River at Pine Bluff, 40 mile below Little Rock.
That would have been more than enough to take care of the timberclad gunboats that were running escort for the supply transports to the Union fleet and Grants army at Vicksburg. As far as I can find her major drawback was her draft. She sat too deep in the water for her to manuver well in the shallow Arkansas River.