Buy a cheap box of blackboard chalk and put it in your toolbox. It will absorb any residual moisture and stop your tools from rusting.
Heat up the nut with a small handheld blowtorch and then hold a candle on the heated metal, allowing the melting wax to infiltrate the thread. The nut will soon become easier to remove as the molten wax lubricates the thread.
The juice from a jar of sweet pickles is excellent for cleaning anything copper. If the ends of copper wiring are showing corrosion, clean them with sweet pickle juice.
BRITTLE NYLON ROPE
If your nylon rope has become hard and brittle with age, soak it in a solution of fabric softener and water to put a spring back in its step.
If your V-belt is broken, you can do a temporary repair on it by using a couple of doubled over lengths of duct tape. This should hold long enough until you are able to make it back to the marina and fit a new V-belt.