This past weekend I just ran new speaker cables to (2) new locations in my boat that sound very similiar to the locations your describing. The speakers will be located directly outside of where captain and passengers feet would be if they are sitting in the helm chairs.
Before starting any wire pulls you will want to be sure you can make the wire route from start to finish to where the speaker will be located.
Gradyfish is right about the owners manual, it shows the pvc chases and runs where you can get wires to about anywhere you need on the boat. These chases penetrate the bulkheads below deck for this purpose and usually end at the plastic inspection plates.
Pop them all open and see what looks like it connects to where, they are all straight runs.
Also make sure you buy substantially more wire than you think you may need, it disappears quickly.
Good luck, what kind of speakers are you installing?