I've been playing the game for almost a month and haven't used the broadside on anything yet. From what I've read and picked up on the help chat, unaimed broadsides requires the [ & ] together. So I tried it in and out of aim mode, just the [ key in and out of aim mode, and the ] key in and out of aim mode.
From what I've read and picked up on the help chat, aim mode needs the left mouse to give the broadside. So just reread the above but replace [ & ] with left mouse. Well that's where I am and any suggestions will be appreciated. Then again, I may simply be doing something wrong myself. LOL I always open to that option. Thanks.