I used a heavy ball on the second try and got him
What Is The Best Ball To Catch Lugia In Soul Silver Instead Of Masterball?
I also used Heavy Ball. Red HP, no status problem. Easy as pie!
Dusk
Net balls or dusk balls if you can't get use ultra balls.Good luck ^.^
Weaken Lugia and then use any ball that you have and keep trying that ball. Eventually you will catch it