Your rod will be fine for a big coho or average (10-20lb spring). I actually like an 8wt better for fish this size. I tend to lose the smaller fish I get more easily than the big ones, I attribute this to the lighter rod flexing more and absorbing more of the fight whereas a stiffer rod (relative to the fish of course) will have less damping and more spring to it....its not necessarily a "springier" rod.... I hope that makes sense. Anyways I'd bet you would do fine with an 8...just make sure you have lots of backing, and don't be afraid to break a fish off if it starts to pull your pants down....you don't want to lose your line.