Mark:
Art is correct. No confederate 3" naval rifle is known to have existed as the confederate production of 3" rifles were intended for the army. If some went to the navy, they were probably taken from the army production. These small field artillery guns were not practical for shipboard use and a gun a this small size was not designed for or called a navy rifle. The 3" size was too small with little application for ship use. The only naval rifle I have heard of were of the larger size columbiads and others.
The federal navy had some 20 and 30 pound Parrotts adapted for naval service by the addition of a shackle to convert the knob for naval service. These were larger then the 3" rifle you mentioned and too heavy for field use. Also, the federal goverment made some Wiard 3.4" rifled boat howitzers intended for the federal navy. They were mounted on special gun carriages for small boat use. If some were captured, they most likely would not have been practical for field use.
Ron