Here's a sampling from Paul H. Silverstone's "Warships of the Civil War Navies (Annapolis, Md.: U.S. Naval Institute Press, 1989):
Union monitors
U.S.S. Monitor (1862), 320 I.H.P.
U.S.S. Weehawken (1863), 320 I.H.P.
U.S.S. Dictator (1864), 3,500 I.H.P.
Other Union ironclads
U.S.S. Keokuk (1862), about 500 I.H.P.
U.S.S. Galena (1862), 800 H.P.
U.S.S. New Ironsides (1862), 700 H.P.
Union screw frigates
U.S.S. Merrimack (1856), 869 I.H.P. as built
U.S.S. Minnesota (1857), 973 I.H.P.
Union screw sloops of war
U.S.S. Hartford (1859), 1,000 I.H.P.
U.S.S. Kearsarge (1862), 842 I.H.P.
Union gunboat
U.S.S. Princeton (1852), 195 H.P.
Confederate ironclads
C.S.S. Albemarle (1864), 400 I.H.P.
C.S.S. Stonewall (1865), 1,200 I.H.P.
Confederate cruiser
C.S.S. Alabama (1862), 600 I.H.P.
By way of comparison, the following from "Conway's All the World's Fighting Ships, 1860-1905" (New York: Mayflower Books, 1979):
French broadside ironclad
Gloire (1860), 2,500 I.H.P.
British armored frigate
H.M.S. Warrior (1861), 5,267 I.H.P.