Here's what I carry
Here's my abbreviated list. I know I forgot many items but this should give you a start.
Boat Essential Tools & Repair Items
General Tools:
Wrenches – Assorted and sized for your vessels nuts and bolts
Flare Wrench’s – Very important for any fuel line work
Drills – 1 Corded and 1 Cordless
Wooden Plugs - One for each thru-hull & tethered to it
LED Head lamp & Flashlights
Hole Saw Kit
Screw Drivers – Assorted
Pick Set – Very Handy
Tap/Die Set – Sized accordingly
Heli-Coil repair kit
Hack Saw – With spare blades
Bolt/Wire Cutters – Big enough to cut rigging
Wire Cutters – Big enough to cut battery cable
Blow Torch – Mini butane type and one standard torch head
Socket Set - SAE and Metric
Pipe Wrenches
Pliers - Various sizes
Water Pump Pliers
Needle Nose Vise Grips - For clamping hoses off etc.
Files – Various
Drill Bits – Full Kit
Countersink - At least two sizes
Sandpaper
Dremel
Rigging Knife's
Calipers
Rigging:
Sewing Kit
Monel Seizing Wire
Sail Repair Tape
1” Nylon Webbing
Sail Slugs – To fit mast track
Sailors Palm, Needles & whipping twine
Clevis Pins – Spares sized for your boat
Cotter Pins – Stainless various sizes
Grommets, Snaps & Twist Locks
Loos Tension Gauge
Dodger fittings
Engine/Plumbing:
Water pump – Complete spare and rebuild kit
Plumbing Fittings – Assorted to match parts on vessel
Zincs – For heat exchanger
Solenoid – Spare
Fuel Pump -Spare
Fuel Line Hose – Min 6 feet all sizes on vessel
Hose barbs – male/male for splicing hoses of various sizes
Impeller – With spare gaskets.
Oil Filter
Oil – for engine
Air filter
Antifreeze
Fuel Filters – Primary and secondary
Fuel Filtering Funnel
Hoses – Min 6 feet each size
Oil absorbing bilge pads (min 10)
Alternator Belts
Thermostat & gaskets
Engine service & parts manuals
Mechanics Manual – For your engine specifically
Hose Clamps – Stainless AWAB type various sizes
Electrical:Inverter – Spare at least 500 watts to power small tools
Electrical Connectors – Assorted marine grade various sizes
Multimeter – Clamp on AC/DC to measure amps, volts and resistance
Heat Shrink – Adhesive lined
Crimper – Ratcheting style for marine grade terminals
Zip Ties
Wire – Assorted gauges 6 feet min per size.
Jumper Wires 10 ga- With alligator clips on each end
Wire Strippers
Light Bulbs – Spares for each socket on the boat
Wire Snake
Terminal strips
Misc:
Turkey baster
Stainless Steel Bar Stock
Aluminum Bar Stock
Stainless Steel Dodger Tubing – short length
Velcro – Regular and industrial grade
Grease – Water proof winch grease
PB Blaster (NOT WD-40

)
BoeShield
Lanocote
TFF Tef Gel
Silicone Caulk
Sika 295UV – Or equivalent
Wet Suit, Mask & Fins, hood
UV Resistant Duct Tape
Stainless Steel - Screws, nuts, bolts, fender washers, nyloc nuts, etc.
Tape – Electrical plus green painters tapes
JB Weld – Or equivalent
Hose – 6 feet minimum for each size on your vessel
C-Clamps
Label maker
Bosuns chair = 2
Spare boat hook = 2
R-134 and charger adapter for refrigeration system
Spare prop, nuts & key
Prop Puller
Emergency tiller
Spare anchors and rodes
Outboard motor fuel line with priming bulb
I know I missed a lot but that should get you going.
A couple of the spare parts bins I carry.