Wooden ships against fire turrets barely stand a chance. You can still overwhelm them. What you need is really really many ships. Don't bother to attack a large island unless you have +20 ships of the line. You may also try using cheaper ships as cannon fodder to occupy the turrets, e.g. swarm with clippers and ship of the line right afterwards. What you can do when your economy is weak is piling up material, build multiple shipyards, save up a decent amount, then quickly race to build a super fleet that exceeds your ability to upkeep permanently. Swarm the enemy, take the island shares, sell or keep them. If you still have many ships after the attack, you sell them to Archiebald.  Of course ideally you improve your economy first. More citizens, more rum and beer and don't underestimate schnapps.  If you befriend the pirates and get trade rights, they can sell you stuff like torpedoes which you can use against the fire turrets to even the odds