Mortars: Use L2 to aim them and R1 to fire. these are great when they are in front of you. I generally do the chain shot first to slow them down a bit, grab the mortar and blast em. farewell half the ship strength.
I generally use the swivel cannons once the boarding has started. Can normally get at least 5/10 enemies down with those. depending on my mood, i'll either go onto the railing and just shoot down whatever i need to finish them off, or if i'm not in a rush, rope swing over. there are a couple ships that require me to go on the other ship, same concept though. i just reload before hopping over if i need it.
I will not hesitate to put my life on the line to keep myself out of harms way. Now Playing: Shadowrun, Skyrim, GTAV, Disgaea D2, AC4:Black Flag.
I always man the swivel gun first, but how I use it differs. If there's a "kill officers" or "kill captain" objective, those targets are my first priority with the cannon. If those objectives don't exist, I primarily aim for killing as many enemies as possible. If there's a "destroy powder stores" objective, I'll kill at least one of them, but I'll try my best to make it clear a few crew members with it.
After clearing the deck, if there are survivors (Against Schooners, this is rare), I'll generally use the nearest rope to swing across - UNLESS there was a "kill scouts" objective, in which case I take the lift up and shoot the scouts down, then cross onto the enemy ship from above.
yupp if i have to kill a certain person, then i take em out first. use all my svivels, headshot some higher level enemies, then get on and battle with my swords. so much i havent tried tho yet, u can have so many tactics.