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.