What you are looking for are bow and stern chasers. They did indeed have guns pointing forward and or/ backward (pointing forward or aft) on ships back then. Not all ships, some ships just fore or aft, some both. A bow chasers was excellent for trying to score a hit upon a target one is pursing. Possibly a hit with a bow gun could know away a piece of rigging and slow your opponent down, hit the helmsman and cause the vessel to veer off course and allow you to catch up, or if you're real lucky hit the rudder and disable it so the enemy you chase cannot control the direction they steer. A stern chaser can help counter ships chasing your vessel. Like the bow chaser, hopes are you might knock away rigging and sails to slow who is chasing you. Maybe you can try and take down bow chasers on the pursuing vessel if they have any.

You might want to go purchase the book The Sea Rover's Practice by Bennerson Little to help yourself out with pirate tactics and combat situations on ships. It is a readable book that has a number of chapters on different topics, making it also a good reference book.

EDIT: One other thing that might be advantageous about these guns (though it applies to both them and the broadsides) is that putting some shots belong the waterline might slow a ship down if they penetrate the hull and cause serious leaking. Leaking causes weight to be added to the vessel, slowing speed, and possibly stopping the vessel if they need to turn the vessel so the injured ship can angle itself so some shots are above the water line when the ship yaws a particular direction and prevents water from getting into the shot holes.