OP still didn't say if he wanted guided or unguided.

For a totally boat based hunt I'd be looking for a boat like this company offers. However, they don't guide, they just transport.

http://www.alaskagoodtimecharters.c...ear_hunting_trips_alaskan_black_bear.asp

This company is fully guided but I don't think I'd want to spend a week on their boat with 4 hunters/guests + crew.

http://alaskablackbearhunts.com/

Google is going to be the OP's best friend, but he'll have to do a lot of legwork or find a good booking agent to do the work. I wouldn't go with anyone that won't provide a client list with contact information. Since the OP wants totally boat based, I'd look for the less traveled destinations and probably avoid POW or Petersburg since these areas are so heavily hunted already.