From StrategyWiki, the free strategy guide and walkthrough wiki

When you've got access to a ship, you can change its armaments by buying and equipping various types of Ship Weapons. Most ports will have a Ship Parts store where you can buy new weapons for your ship, as well as repair kits and other upgrades.

Guns for your ship fall into three categories: Main Cannons, Secondary Cannons, and Torpedoes. There are also S. Cannons, but those cannot be changed or upgraded.

Ship Weapons are equipped by pressing to open the menu, selecting the ship slot, and clicking on the weapon slot you wish to change. A list of the available weapons for that slot will appear, as well as a description of the cannon or torpedo and its changes to the ship stats.

[edit] Main Cannons

Main Cannons are the most powerful standard cannons you can get for your ship and require the most Spirit Points to fire, but they only attack for a single turn.

Main Cannon At: 35, Hi: 80, Sp: 4, Limit: 0
The Little Jack's main cannon. It's rather old, but Drachma has kept it in great shape.
Equippable on the Little Jack.

Standard Cannon At: 40, Hi: 83, Sp: 4, Limit: 0
The standard cannon on Valuan warships, sometimes available on the Black Market.
Equippable on the Little Jack.

[edit] Secondary Cannons

Secondary Cannons use less Spirit Points and are less powerful than Main Cannons, but can fire for more than one consecutive turn per round. They can often be more accurate than Main Cannons.

Cannon list goes here - to be created

[edit] Torpedoes

Like Secondary Cannons, Torpedoes use less Spirit Points than Main Cannons, but fire in a different way. You have to choose when to fire the torpedo, and you can also decide when it hits the other ship - you can even spread it across rounds, depending on the range of the torpedo.

Cannon list goes here - to be created