Hi guys!
My sacs tomahawk s590 ( not so common brand? ) has quite nice storage space and I have there:
spark plugs+wrench
water separator/fuel filter
20ltrs gasoline
anchor and rope 40mtrs + 30mtrs
paddle, fire-extinquisher
screw drivers, hex-drivers
wrench-set, adjustable wrench
crimpers + connectors, other pliers
knife
cable-ties
prop nut set, extra sockets for prop nut
good torch/flashlight
duck-tape, electrical tape
first aid-kit
clamp-seal, electrical pump
immersion suits and life-jackets
and also SPARE PROP. Unfortunately in Finland there is some scrap on the sea at spring time: pieces of wood, empty bottles etc. because when ice is melting away it brings scrap from islands. Also my spare prop is with 2" less pitch if there is a need to take more load on the boat. Ok it´s not fun to change prop on the sea but if you have to you can!
We use my RIB mainly to go to summer house at off-shore island 24km from main land. When going there or coming back with not best weather conditions you want to have spares/tools/spare prop with you...