1666 is a set of free wargames rules for naval combat in the Anglo Dutch wars. The game is designed for 1/2400 ships on a 2 inch hex grid. Direct download.
naval
WWII Naval Rules
Gettysburg Gamers offer a set of free wargames rules for WWII navies.
High Seas Drifter WWII Era Battleship Rules
High Seas Drifter is a set of free wargames rules for playing battleship combats in the World War II era.
Steel Ships and Iron Iron Hearts Pre-Dreadnought Rules
Steel Ships and Iron Hearts is a set of free wargames rules for pre-dreadnought naval combat. The rules set dates to 1982 and was played by the Olympic Wargaming league. Classic stuff.
Battle of the Yellow Sea Scenario
My friend Jim loves to run dreadnaught era naval miniature wargames. Here’s a good scenario for the Battle of the Yellow Sea from Bill Madison of the Naval Wargames Society.