On ships such as the Santa Maria, what was usually mounted on board to help defend them from enemy ships?

Question

ships of that era

Answer 1

muzzle loading cannons

Answer 2

On the bow of every old sea-going vessel was a statue of a mermaid or female to help protect and guide.According to religion and local beliefs.Or the queen?

Answer 3

muzzle loading cannon of various types and sizes. from large shotgun type cannons to large cannon that shot 32 pound cannon balls. the crew would use pistols and rifles usually muskets or match locks. when that failed they would use knives swords axes and clubs.

Answer 4

It's very likely it had no armament.  Firstly it was a coastal vessel, only 70' long, never designed for exploration.  Secondly where they were sailing they would not expect to encounter other ships.

They very possibly had a small cannon used for signaling but may have been useful to some extent especially to scare natives.

The worst ongoing threat to Caribbean shipping was pirates but they came along later when commerce was well established.

In the early and mid 1400's, the British achieved superiority in the mediteranean with cannons similar to those found on shore.  However they had to be mounted on heavy trucks or wheeled carriages, so they could be rolled inward for reloading.  (Truck and carriage are terms and not trucks and carriages as we normally think of seeing in the roads.)  Their heavy ships designed to survive the Atlantic were capable of carrying significant weapons compared to the light vessels of the Turks and Ottoman empire.

The Chinese similarly used cannons on their seagoing Junks and dominated the Indian Ocean and South China Sea.

I hope this helps.