Assassin's Creed 4: Black Flag Walkthrough Part 40 – Sequence 7 “The Fireship”

Optional Objectives:
Use the mortar to sink 3 ships
Use a fire barrel to sink a ship

Head to the marker on the beach. You will find Vane and Rackham there waiting for Kenway. You need to clear out the galleon of the soldiers before you can break away from the blockade. Time for some naval action and it is going to be intense, if short.

The moment the Gunships appear is the same moment you want to start working at the optional objective of the Mortar Fire. There are 2 small groups of 3 Gunboats coming at you. A good round of Mortar Fire will easily take out 2 or 3 of them. Otherwise, just focus on using Mortar fire to take out the ships. Remember to lead the shot because of the delay between firing and impact. This is the only time you can really stray from the Fireship. Still, it is much better to stay close.

Once you have dealt with the first 2 groups of Gunboats return to the Fireship. There are more  gunboats that will close in. This is the best time to continue onto the second objective. You need to watch for a gunboat to get behind the Jackdaw. This is your chance to down a fire barrel on them and take them out. After that just stay by the fire ship and it goes into the blockade. When it does make it, you have to just make it to the marker. It is much better to just run from the fighting. While the larger ships can be taken, it is hardly work the effort to do so.

When you make it clear, you are done with the sequence and the memory. Time to move forward in Edward Kenway's life.