Use a text editor such as notepad to edit the "shiptypes" file in the "\Program Files\Paradox Interactive\East India Company\Data\AI" directory. This file contain the configuration of every ship. You can edit their price, health, cannons, cargo space, etc. This procedure may affect AI game play, because the AI may use these same configurations to purchase and use their ships of the same kind. The following is an example for the Galleon.
galleon
{
// name from locale
type = str_SHIP_TYPE_GALLEON