Control cables are a fairly easy job. First of all, make sure the outboards are in neutral. Remove the starboard side lower engine cowling on each motor (this is not mandatory as far as I remember, but it certainly makes it a little easier disconnected the cable ends from the linkages). Remove the clamps holding down the threaded cable length adjustment knob. This is the knob towards each cable end that has a larger diameter "toothed" plastic disc. Disconnect the cable ends from the shift and throttle linkages. Now up at the helm unbolt/unscrew your binnacle controls from the dash. You will have to disconnect the trim switch harness wires (should be two three-wire connectors for duals I believe). Depending on how much slack you have in your wiring you may get the clearance you need without disconnecting the start-in-gear protection circuit wires (yellow wire with red stripe). Otherwise you will either have to disconnect them if they are bullet connectors or such, or as I had to do when they were connected to the harness with a butt-splice, you will have to cut and reconnect.
Lift binnacle off of dash. You may need to give yourself some slack in the control cables to do this, and since they are now disconnected at the engines, it should not be an issue. I do not know which style binnacle you have, but disconnecting the cables there is relatively straightforward. Just make sure to pay attention to shift vs. throttle cables, and mark which side does which. There is not any adjustment that can be done at the binnacle side of things, so that is essentially plug and play.
With everything disconnected, pull the disconnected cables through the tunnel from the binnacle side, one at a time. As you pull them out, mark what they were (ie starboard port motor and shift/throttle). Before you pull the last cable through, duct tape a piece of heavy gauge wire to the end of it that is at least as long as what the cable is, this will be assist you in pulling through the new cables, as pushing them through either fwd-aft or aft-fwd will likely not work or be extremely frustrating as they will get caught on everything along the way.
With the cables out, you will need to measure the length of each cable to the nearest foot. These are the measurements you will need to order new units. Installation is essentially the reverse of dissasembly. Once the cables are fed through the boat, connect at the binnacle first. Make sure the binnacle is still in neutral with no throttle advance. When you are connecting them at the outboards, this is where adjustment of that disk knob comes into play. With the cables disconnected still, grasp the shift linkage with your hand. Since it is in neutral there should be a slight amount of play in the linkage. You want your cable to connect at the linkage with the linkage at the "center" of that free play. If it ends up favoring one direction or the other, it may cause you to not fully shift into reverse or forward which will cause excessive wear of the clutch dog in the lower unit. Adjustment is accomplished by threading that knob forward or back on the cable.
Adjusting the throttle cables is done in a similar manner. Someone can correct me if I am wrong, but with the throttle fully pulled back to idle, the roller cam on the throttle linkage should not have any preload (ie should just be out of contact with the upper part of the linkage). In order to get the throttle handles to line up, I assume you may have to do some fine-tuning on the water. Keep the cowlings off, and bring a wrench. It is not very difficult to adjust them once everything is hooked up with the cowling on.
