I don't know what happened to my post about the key and the thru-hull caps, but for others and future reference.... The water/fuel/waste caps are all the same thread and size. So, you could get a new cap and not need the smaller wrench- "one wrench fits all". Maybe even get a cap in case one falls overboard. I noticed the screw that holds the chains on the caps can come off and fall into the tanks. I had previously taken the chain off the water cap, but will also do the fuel one.