Hi fellow '09 270 owner!
I carry on board only the basics as I would only do basic repairs; i.e. tightening alternator belt/tensioner. I picked up at Canadian Tire a JobMate toolkit (canvas bag, sockets, allen/hex keys, wrenches, screwdriver (w/ bits), hammer, flashlight, pliers, box cutter) and I added wire cutter/stripper/crimper, electrical connectors/wire, electrical tape, quick ties, duct tape, and utility scissors. That takes care of any impromptu repairs. Having spare parts on hand for more in depth repairs depends where and how long the voyage will be, away from civilization this is. In my case almost never.
However, on my first time out I blew a fuse (the bilge hatch) and was low on gear lube (air bubble?) so I added to my list one of every fuse type in the panel and spare bottles of every fluid. Of course, having the manuals handy for error codes and such is important too.
For me I created a departure checklist to remind myself to check engine fluid levels, strainers, navigation lights, GPS/charts, radio, and safety equipment.
As for safety equipment I have, in addition to the safety kit required by law, a (large) first aid kit, gas powered horn, extra batteries, electric lantern, flare gun, axe, lighter/matches, safety blanket, FRS radio(s), and small fire extinguisher. I include in the bag once underway a float plan, vessel registration (other documents), contact information, and money. All of this stuff I put into a waterproof/floating/survival bag easily accessible in the cockpit.
Hope this helps & cheers,
Kaoru