A Hotter Fire is a set of free wargames rules for naval combat between civil war ironclads.
ironclads
Ironclad American Civil War Naval Rules
From the Naval Wargames Association comes Ironclad, a set of free wargames rules for ACW ironclads.
Steam Iron and Tin ACW Naval Rules
Steam Iron and Tin is a set of 15mm ACW naval rules that was distributed to people who attended the 1985 Origins Convention in Baltimore (I was at that convention!).
Ironclad Draughts One Page Ironclad Rules
Ironclad Draughts is a set of one-page rules for playing out battles between ironclads.
Civil War Ironclads Gaming Page
The Jackson Gamers have a page with everything you need to know to start gaming Civil War Ironclads