A fairly complete tool kit would include:
Mechanics tools like:
A
Craftsman mechanics set,-
this includes both metric and imperial, since I've found on my boat there is a mix... the outboards use metric, the rest of the boat is pretty much imperial
Several assorted visegrips
Several assorted screwdrivers, including torx, allen, flat and phillips blades
A large set of channel locks
A pipe wrench
A hacksaw
Some chisels-wood and metal,
A few drift punches
A small sledge,
A ball peen hammer,
A few assorted files and rasps
A set of calipers
A tape measure
A strap wrench
An oil filter wrench
Electrical kit that includes:
A multimeter,
An electrical terminal crimping tool,
A butane torch for heat shrink terminals
Assorted heat shrink terminals
Some assorted wire in red and yellow, 12 AWG is a very useful size.
Electrical tape, a good brand, like 3M
Spare fuses for any carried aboard
A rigging kit that contains:
Spare clevis pins, cotter rings and cotter pins
Some small line, say 1/8-1/4" for various repairs, lashings, messenger lines, etc.
A sailmaker's palm
Spare sailcloth
Sail repair tape
Sailmaker's needles
Sail repair thread
Some stainless steel rings
Whipping twine
Beeswax
A couple of spare blocks of the most common kind used on your boat
A bosun's chair
A good awl
A repair kit that contains:
3M 5200 Fast Cure
3M 4000 UV
Lanocote
Loctite (both red and blue)
Some epoxy putty that sets underwater. Progressive Epoxy Polymers has some really good stuff.
Boeshield T9
McLube SailKote
Some regular epoxy resin and hardener
PBlaster
Heavy waterproof bearing grease
Some fiberglass cloth
Some colloidial fumed silica (Cabo-sil) for thickening the epoxy
Some disposable gloves-nitrile preferably
Respirator mask
Some mixing supplies-cups, containers, sticks, etc.
Acetone
Denatured Alcohol
Teflon Tape
Plumber's Putty
A roll of butyl tape
Rescue tape or some other self-fusing silicone tape
A roll of duct tape
Spares
Spark plugs for your outboard motors
Fuel and oil filters
Impellers for the various pumps aboard
An assortment of stainless steel screws, nuts and washers
Shear pin for outboard motor
Props for outboard motors, or spare blades if using a modular composite prop like a Pirahna
Miscellaneous Tools I've found very useful:
A pocket multitool, like the Leatherman Core or Surge
A cordless toolset including a drill, a sawzall, a jigsaw and a circular saw is often very useful
Battery lug crimping tool
Several flashlights, including a headlamp
A dremel rotary tool is often useful
A set of taps and dies
A pop rivet tool with aluminum and stainless steel rivets up to 3/16" in diameter