Ship's Howitzers is a technology in Age of Empires III that can be researched by European and Asian civilizations at the Dock once the Industrial Age is reached. Once researched, it upgrades Monitors to Heavy Monitors, which have +25% hit points and attack damage. In the Definitive Edition, it is also available to the United States and Mexicans, but for these two civilizations, it upgrades Ironclads to Heavy Ironclads, which have +25% hit points and attack damage.
Gill Nets · 
Long Lines · 
Armor Plating · 
Carronade · 
Percussion Lock · 
Ship's Howitzers
Improved Cordage*** · 
River Raids*** · 
Rawhide Covers (
) · 
Flaming Arrows (
) · 
Cipactli Worship (
) · 
Totora Reeds (
)*
River Skirmishes · 
Heavy Riverboats