When you are offshore in a boat, you want to use a heavier fly rod. A 9, 10, 11, or 12. You need the muscle and you need the butt section of that rod to fight a fish when it gets close to the boat. If it sounds, you need to be able to lift the fish, and you also need a heavier line. You want that 9, 10, 11, or 12-weight line because you are throwing bigger flies generally offshore, and you almost always have wind. So a 9, 10, 11, or 12-weight line works best, because an 8-weight is a little risky once you get offshore. You really want a bigger reel when you are offshore fly fishing. You need a strong drag because these fish can go a long way. You need a reel that's big enough to hold at least hold 200 yards of backing. You need a large arbor reel also because the fish may run at you and you want to be able to gather that line quickly. Large arbor reels with their bigger diameter will bring in line quicker.
You should also get the best reel you can afford with the strongest drag system. A fast-running fish can literally heat up an inferior drag system so much that the drag surfaces melt, and the reel begins to smoke. Choose your fly rod based on the size of the fish and the size of the flies you will be using. 9-weight is fine for a fish up to about 25 lbs, but if you plan on casting a giant popper all day you might want to choose a heavier 10 or 11-weight line to push that big fly out there. 12-weight rods are reserved for fighting very big fish like Tarpon and Tuna. Fly rods are even made up to a massive 14-weight pool cue, which is used for marlin and other giant fish.