must-haves
The longer the voyage, the longer the list of must-have spares, but here's what I'd consider essential for a short hop:Spares: raw-water impellor for engine; alternator belt; fuel filters (two of each); fuses; a back-up bilge pump; a second VHF and GPS; spare prop.In terms of tools, carry a bolt cutter in case the rig goes down, and an electrical kit with connectors, crimper, circuit tester, et cetera. You should have some sort of mallet onboard with tapered soft-wood plugs for failed thru-hulls. Take an assortment of spare hose clamps. Have whatever tools you need to bleed the engine, adjust engine mounts, tune rigging turnbuckles et cetera. I always carry a few extra circuit breakers for the control panel. Have an assortment of cotter pins, bolts and screws. Carry a sail repair kit, complete with sticky tape. Always have a roll of riggers tape onboard. As Colin suggested, I always carry a head rebuild kit, and a spare macerator impellor. THE ABOVE LIST IS NOT EXHAUSTIVE. I'm sure others will add what I've forgotten.