8lb would probably be fine on the right rod and reel setup.

For example, an experienced angler can take a 15lb steely on 4lb line with about a 10ft noodle rod (and not play it until it's about dead!!).

Are the fish you are targeting line shy? Will you be using a down rigger (sounds like you'll need to)?

If you do go with lighter line, just make sure you have your spool set up with enough line and your drag in good working shape...