On Rhapsody I may err on the side of conservative to be able to fix stuff. I have everyday onboard tools / parts and extra stuff I take when cruising.
Here is what I consider essential to have:
- Screw drivers - 2 flat head and 2 phillips head (small & large)
- Adjustable end wrench medium 8"
- Sharp knife
- socket wrench set both SAE and metric (I think it's ~ 25 piece set with ratchet and extensions) - Yanmar has both standards
- roll of duct tape for emergency repair
- a bunch of ty-wraps
- small tube of sealant & epoxy for emergency repairs
- Leatherman multi-tool (cutters, needle nose pliers, file)
Check this page and download the excel spreadsheet "Recommended Onboard Engine Spares with Part Numbers (Excel Spreadsheet)"
My guess is there is less than 8 pounds of stuff stored low in the boat.