Wheel bearings or hub assembly. Ask me how I know
Tell me about it! I was driving back from Alabama two years ago. I had a bearing go bad. Lost the wheel, hub, everything. Just like your picture.
The funny thing? I had no clue it happened until I unhooked my boat at home and noticed the trailer leaning. Thanks goodness for dual axles and a properly balanced trailer.
Other than the stuff already mentioned..
Dude Wipes
Headlamp
Safety glasses (for running at night or in rain when it's too dark for sunglasses)
Basic tools - screwdriver, adjustable wrench..
Spare trolling motor prop & pin (make sure you have the tools to remove the old prop if necessary)
Basic first aid. I recently put together a list to make my own box instead of buying kits that have crap you don't need. Can easily make several boxes and put on vehicles, give to friends, or sell them for a few bucks to help break even.
I welcome any suggestions if I've overlooked anything.
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70% rubbing alcohol
Adhesive tape
Antiseptic spray
Gauze
Bandaids
Butterfly bandages
Bandages
Braid (for hook removal)
Hook cutters
Tylenol/aspirin/ibuprofen
New skin/super glue
Gloves
Scissors
Tweezers
Hand sanitizer
Cotton balls
Eye wash
Syringe
Anti diarrhea
Antacids
Hydrocortisone cream
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Various size zip ties - including really big ones (if PowerPole pump goes out and pole won't stay up).
Candy/snack with high sugar content. Can help a diabetic out (I've been asked before and was glad I had something).
Rope.
If you carry a prop, better have a prop wrench, hub, and spare washers in case you drop any.