I can help you, in two ways...
1) This section is for discussion about Liberty City Stories
, the discussion for Ballad Of Gay Tony
can be found here
2) If you can destroy the yacht, you should be able to destroy the boats.
Only thing I can really say, is to select the "bumper" view (by pressing Back/Select a few times) which - atleast to me - is easier to aim with.
Just keep firin' and keep tryin', you'll get it.