Saw this and thought of a couple more to add to stowage list that i don't see here.

Trash bags.... priceless when you need one
Koozies
Apirin.. if not in first aid kit
sunscreen

Tell someone close where ur going & when ur comin back! Stay in touch w/someone on land!
SPF #30---
Xtra sunglasses---
Duct tape---
Watertight container 4 phone if you hav to swim with it!

I also carry a 3 million candle power spot light and extra plug and a few of the drain plugs for the exhaust w/orings ..

KNOWLEDGE!

Take a boating course, and, if possible check into "basic marine maintainance" courses offered through some Gov't agencies and/or colleges.

Face it, having all the spare parts in the world and a roller cabinet full of Snap On tools does you NO good whatsoever if you have no idea whats wrong, how to fix it, or how to diagnose whats wrong.

A float plan is a also a great idea, most smart phones have a free app. that allows you to file a plan and Email it to whoever you want, it includes your boat Reg numbers, name, etc, so, if [God Forbid] something happens and you need assistance, all your pertinent info will be available.

Its also a good idea to have "someone" on the boat with a good knowledge of how to operate the boat, and most importantly the radio, again, you can take a "VHF course" from several places. If "you" are injured or get sick, fall overboard, pass out, etc. Its a good idea to have someone who knows "what to do" [other than get hysterical and start screaming and crying, lol]

Just my 2 cents!
Michael

it is essential that you teach your wife or s/o basic operations of the boat, and basic navigation, and basic vhf function. If god forbid something happened to you she could safely get you back to port.